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         protected function wasQueryTimeout( $error, $errno ) {
 490                 return $errno == 2062;
 491         }
 492
 493         /**
 494          * @param string $table
 495          * @param array $uniqueIndexes
 496          * @param array $rows
 497          * @param string $fname
 498          * @return ResultWrapper
 499          */
 500         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
 501                 return $this->nativeReplace( $table, $rows, $fname );
 502         }
 503
 504         /**
 505          * Estimate rows in dataset
 506          * Returns estimated count, based on EXPLAIN output
 507          * Takes same arguments as Database::select()
 508          *
 509          * @param string|array $table
 510          * @param string|array $vars
 511          * @param string|array $conds
 512          * @param string $fname
 513          * @param string|array $options
 514          * @return bool|int
 515          */
 516         public function estimateRowCount( $table, $vars = '*', $conds = '',
 517                 $fname = __METHOD__, $options = []
 518         ) {
 519                 $options['EXPLAIN'] = true;
 520                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 521                 if ( $res === false ) {
 522                         return false;
 523                 }
 524                 if ( !$this->numRows( $res ) ) {
 525                         return 0;
 526                 }
 527
 528                 $rows = 1;
 529                 foreach ( $res as $plan ) {
 530                         $rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
 531                 }
 532
 533                 return (int)$rows;
 534         }
 535
 536         public function tableExists( $table, $fname = __METHOD__ ) {
 537                 // Split database and table into proper variables as Database::tableName() returns
 538                 // shared tables prefixed with their database, which do not work in SHOW TABLES statements
 539                 list( $database, , $prefix, $table ) = $this->qualifiedTableComponents( $table );
 540                 $tableName = "{$prefix}{$table}";
 541
 542                 if ( isset( $this->mSessionTempTables[$tableName] ) ) {
 543                         return true; // already known to exist and won't show in SHOW TABLES anyway
 544                 }
 545
 546                 // We can't use buildLike() here, because it specifies an escape character
 547                 // other than the backslash, which is the only one supported by SHOW TABLES
 548                 $encLike = $this->escapeLikeInternal( $tableName, '\\' );
 549
 550                 // If the database has been specified (such as for shared tables), use "FROM"
 551                 if ( $database !== '' ) {
 552                         $encDatabase = $this->addIdentifierQuotes( $database );
 553                         $query = "SHOW TABLES FROM $encDatabase LIKE '$encLike'";
 554                 } else {
 555                         $query = "SHOW TABLES LIKE '$encLike'";
 556                 }
 557
 558                 return $this->query( $query, $fname )->numRows() > 0;
 559         }
 560
 561         /**
 562          * @param string $table
 563          * @param string $field
 564          * @return bool|MySQLField
 565          */
 566         public function fieldInfo( $table, $field ) {
 567                 $table = $this->tableName( $table );
 568                 $res = $this->query( "SELECT * FROM $table LIMIT 1", __METHOD__, true );
 569                 if ( !$res ) {
 570                         return false;
 571                 }
 572                 $n = $this->mysqlNumFields( $res->result );
 573                 for ( $i = 0; $i < $n; $i++ ) {
 574                         $meta = $this->mysqlFetchField( $res->result, $i );
 575                         if ( $field == $meta->name ) {
 576                                 return new MySQLField( $meta );
 577                         }
 578                 }
 579
 580                 return false;
 581         }
 582
 583         /**
 584          * Get column information from a result
 585          *
 586          * @param resource $res Raw result
 587          * @param int $n
 588          * @return stdClass
 589          */
 590         abstract protected function mysqlFetchField( $res, $n );
 591
 592         /**
 593          * Get information about an index into an object
 594          * Returns false if the index does not exist
 595          *
 596          * @param string $table
 597          * @param string $index
 598          * @param string $fname
 599          * @return bool|array|null False or null on failure
 600          */
 601         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 602                 # SHOW INDEX works in MySQL 3.23.58, but SHOW INDEXES does not.
 603                 # SHOW INDEX should work for 3.x and up:
 604                 # https://dev.mysql.com/doc/mysql/en/SHOW_INDEX.html
 605                 $table = $this->tableName( $table );
 606                 $index = $this->indexName( $index );
 607
 608                 $sql = 'SHOW INDEX FROM ' . $table;
 609                 $res = $this->query( $sql, $fname );
 610
 611                 if ( !$res ) {
 612                         return null;
 613                 }
 614
 615                 $result = [];
 616
 617                 foreach ( $res as $row ) {
 618                         if ( $row->Key_name == $index ) {
 619                                 $result[] = $row;
 620                         }
 621                 }
 622
 623                 return empty( $result ) ? false : $result;
 624         }
 625
 626         /**
 627          * @param string $s
 628          * @return string
 629          */
 630         public function strencode( $s ) {
 631                 return $this->mysqlRealEscapeString( $s );
 632         }
 633
 634         /**
 635          * @param string $s
 636          * @return mixed
 637          */
 638         abstract protected function mysqlRealEscapeString( $s );
 639
 640         public function addQuotes( $s ) {
 641                 if ( is_bool( $s ) ) {
 642                         // Parent would transform to int, which does not play nice with MySQL type juggling.
 643                         // When searching for an int in a string column, the strings are cast to int, which
 644                         // means false would match any string not starting with a number.
 645                         $s = (string)(int)$s;
 646                 }
 647                 return parent::addQuotes( $s );
 648         }
 649
 650         /**
 651          * MySQL uses `backticks` for identifier quoting instead of the sql standard "double quotes".
 652          *
 653          * @param string $s
 654          * @return string
 655          */
 656         public function addIdentifierQuotes( $s ) {
 657                 // Characters in the range \u0001-\uFFFF are valid in a quoted identifier
 658                 // Remove NUL bytes and escape backticks by doubling
 659                 return '`' . str_replace( [ "\0", '`' ], [ '', '``' ], $s ) . '`';
 660         }
 661
 662         /**
 663          * @param string $name
 664          * @return bool
 665          */
 666         public function isQuotedIdentifier( $name ) {
 667                 return strlen( $name ) && $name[0] == '`' && substr( $name, -1, 1 ) == '`';
 668         }
 669
 670         public function getLag() {
 671                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 672                         return $this->getLagFromPtHeartbeat();
 673                 } else {
 674                         return $this->getLagFromSlaveStatus();
 675                 }
 676         }
 677
 678         /**
 679          * @return string
 680          */
 681         protected function getLagDetectionMethod() {
 682                 return $this->lagDetectionMethod;
 683         }
 684
 685         /**
 686          * @return bool|int
 687          */
 688         protected function getLagFromSlaveStatus() {
 689                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 690                 $row = $res ? $res->fetchObject() : false;
 691                 if ( $row && strval( $row->Seconds_Behind_Master ) !== '' ) {
 692                         return intval( $row->Seconds_Behind_Master );
 693                 }
 694
 695                 return false;
 696         }
 697
 698         /**
 699          * @return bool|float
 700          */
 701         protected function getLagFromPtHeartbeat() {
 702                 $options = $this->lagDetectionOptions;
 703
 704                 if ( isset( $options['conds'] ) ) {
 705                         // Best method for multi-DC setups: use logical channel names
 706                         $data = $this->getHeartbeatData( $options['conds'] );
 707                 } else {
 708                         // Standard method: use master server ID (works with stock pt-heartbeat)
 709                         $masterInfo = $this->getMasterServerInfo();
 710                         if ( !$masterInfo ) {
 711                                 $this->queryLogger->error(
 712                                         "Unable to query master of {db_server} for server ID",
 713                                         $this->getLogContext( [
 714                                                 'method' => __METHOD__
 715                                         ] )
 716                                 );
 717
 718                                 return false; // could not get master server ID
 719                         }
 720
 721                         $conds = [ 'server_id' => intval( $masterInfo['serverId'] ) ];
 722                         $data = $this->getHeartbeatData( $conds );
 723                 }
 724
 725                 list( $time, $nowUnix ) = $data;
 726                 if ( $time !== null ) {
 727                         // @time is in ISO format like "2015-09-25T16:48:10.000510"
 728                         $dateTime = new DateTime( $time, new DateTimeZone( 'UTC' ) );
 729                         $timeUnix = (int)$dateTime->format( 'U' ) + $dateTime->format( 'u' ) / 1e6;
 730
 731                         return max( $nowUnix - $timeUnix, 0.0 );
 732                 }
 733
 734                 $this->queryLogger->error(
 735                         "Unable to find pt-heartbeat row for {db_server}",
 736                         $this->getLogContext( [
 737                                 'method' => __METHOD__
 738                         ] )
 739                 );
 740
 741                 return false;
 742         }
 743
 744         protected function getMasterServerInfo() {
 745                 $cache = $this->srvCache;
 746                 $key = $cache->makeGlobalKey(
 747                         'mysql',
 748                         'master-info',
 749                         // Using one key for all cluster replica DBs is preferable
 750                         $this->getLBInfo( 'clusterMasterHost' ) ?: $this->getServer()
 751                 );
 752
 753                 return $cache->getWithSetCallback(
 754                         $key,
 755                         $cache::TTL_INDEFINITE,
 756                         function () use ( $cache, $key ) {
 757                                 // Get and leave a lock key in place for a short period
 758                                 if ( !$cache->lock( $key, 0, 10 ) ) {
 759                                         return false; // avoid master connection spike slams
 760                                 }
 761
 762                                 $conn = $this->getLazyMasterHandle();
 763                                 if ( !$conn ) {
 764                                         return false; // something is misconfigured
 765                                 }
 766
 767                                 // Connect to and query the master; catch errors to avoid outages
 768                                 try {
 769                                         $res = $conn->query( 'SELECT @@server_id AS id', __METHOD__ );
 770                                         $row = $res ? $res->fetchObject() : false;
 771                                         $id = $row ? (int)$row->id : 0;
 772                                 } catch ( DBError $e ) {
 773                                         $id = 0;
 774                                 }
 775
 776                                 // Cache the ID if it was retrieved
 777                                 return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
 778                         }
 779                 );
 780         }
 781
 782         /**
 783          * @param array $conds WHERE clause conditions to find a row
 784          * @return array (heartbeat `ts` column value or null, UNIX timestamp) for the newest beat
 785          * @see https://www.percona.com/doc/percona-toolkit/2.1/pt-heartbeat.html
 786          */
 787         protected function getHeartbeatData( array $conds ) {
 788                 // Query time and trip time are not counted
 789                 $nowUnix = microtime( true );
 790                 // Do not bother starting implicit transactions here
 791                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
 792                 try {
 793                         $whereSQL = $this->makeList( $conds, self::LIST_AND );
 794                         // Use ORDER BY for channel based queries since that field might not be UNIQUE.
 795                         // Note: this would use "TIMESTAMPDIFF(MICROSECOND,ts,UTC_TIMESTAMP(6))" but the
 796                         // percision field is not supported in MySQL <= 5.5.
 797                         $res = $this->query(
 798                                 "SELECT ts FROM heartbeat.heartbeat WHERE $whereSQL ORDER BY ts DESC LIMIT 1"
 799                         );
 800                         $row = $res ? $res->fetchObject() : false;
 801                 } finally {
 802                         $this->restoreFlags();
 803                 }
 804
 805                 return [ $row ? $row->ts : null, $nowUnix ];
 806         }
 807
 808         protected function getApproximateLagStatus() {
 809                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 810                         // Disable caching since this is fast enough and we don't wan't
 811                         // to be *too* pessimistic by having both the cache TTL and the
 812                         // pt-heartbeat interval count as lag in getSessionLagStatus()
 813                         return parent::getApproximateLagStatus();
 814                 }
 815
 816                 $key = $this->srvCache->makeGlobalKey( 'mysql-lag', $this->getServer() );
 817                 $approxLag = $this->srvCache->get( $key );
 818                 if ( !$approxLag ) {
 819                         $approxLag = parent::getApproximateLagStatus();
 820                         $this->srvCache->set( $key, $approxLag, 1 );
 821                 }
 822
 823                 return $approxLag;
 824         }
 825
 826         public function masterPosWait( DBMasterPos $pos, $timeout ) {
 827                 if ( !( $pos instanceof MySQLMasterPos ) ) {
 828                         throw new InvalidArgumentException( "Position not an instance of MySQLMasterPos" );
 829                 }
 830
 831                 if ( $this->getLBInfo( 'is static' ) === true ) {
 832                         return 0; // this is a copy of a read-only dataset with no master DB
 833                 } elseif ( $this->lastKnownReplicaPos && $this->lastKnownReplicaPos->hasReached( $pos ) ) {
 834                         return 0; // already reached this point for sure
 835                 }
 836
 837                 // Call doQuery() directly, to avoid opening a transaction if DBO_TRX is set
 838                 if ( $this->useGTIDs && $pos->gtids ) {
 839                         // Wait on the GTID set (MariaDB only)
 840                         $gtidArg = $this->addQuotes( implode( ',', $pos->gtids ) );
 841                         $res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
 842                 } else {
 843                         // Wait on the binlog coordinates
 844                         $encFile = $this->addQuotes( $pos->file );
 845                         $encPos = intval( $pos->pos );
 846                         $res = $this->doQuery( "SELECT MASTER_POS_WAIT($encFile, $encPos, $timeout)" );
 847                 }
 848
 849                 $row = $res ? $this->fetchRow( $res ) : false;
 850                 if ( !$row ) {
 851                         throw new DBExpectedError( $this,
 852                                 "MASTER_POS_WAIT() or MASTER_GTID_WAIT() failed: {$this->lastError()}" );
 853                 }
 854
 855                 // Result can be NULL (error), -1 (timeout), or 0+ per the MySQL manual
 856                 $status = ( $row[0] !== null ) ? intval( $row[0] ) : null;
 857                 if ( $status === null ) {
 858                         // T126436: jobs programmed to wait on master positions might be referencing binlogs
 859                         // with an old master hostname. Such calls make MASTER_POS_WAIT() return null. Try
 860                         // to detect this and treat the replica DB as having reached the position; a proper master
 861                         // switchover already requires that the new master be caught up before the switch.
 862                         $replicationPos = $this->getReplicaPos();
 863                         if ( $replicationPos && !$replicationPos->channelsMatch( $pos ) ) {
 864                                 $this->lastKnownReplicaPos = $replicationPos;
 865                                 $status = 0;
 866                         }
 867                 } elseif ( $status >= 0 ) {
 868                         // Remember that this position was reached to save queries next time
 869                         $this->lastKnownReplicaPos = $pos;
 870                 }
 871
 872                 return $status;
 873         }
 874
 875         /**
 876          * Get the position of the master from SHOW SLAVE STATUS
 877          *
 878          * @return MySQLMasterPos|bool
 879          */
 880         public function getReplicaPos() {
 881                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 882                 $row = $this->fetchObject( $res );
 883
 884                 if ( $row ) {
 885                         $pos = isset( $row->Exec_master_log_pos )
 886                                 ? $row->Exec_master_log_pos
 887                                 : $row->Exec_Master_Log_Pos;
 888                         // Also fetch the last-applied GTID set (MariaDB)
 889                         if ( $this->useGTIDs ) {
 890                                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_slave_pos'", __METHOD__ );
 891                                 $gtidRow = $this->fetchObject( $res );
 892                                 $gtidSet = $gtidRow ? $gtidRow->Value : '';
 893                         } else {
 894                                 $gtidSet = '';
 895                         }
 896
 897                         return new MySQLMasterPos( $row->Relay_Master_Log_File, $pos, $gtidSet );
 898                 } else {
 899                         return false;
 900                 }
 901         }
 902
 903         /**
 904          * Get the position of the master from SHOW MASTER STATUS
 905          *
 906          * @return MySQLMasterPos|bool
 907          */
 908         public function getMasterPos() {
 909                 $res = $this->query( 'SHOW MASTER STATUS', __METHOD__ );
 910                 $row = $this->fetchObject( $res );
 911
 912                 if ( $row ) {
 913                         // Also fetch the last-written GTID set (MariaDB)
 914                         if ( $this->useGTIDs ) {
 915                                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_binlog_pos'", __METHOD__ );
 916                                 $gtidRow = $this->fetchObject( $res );
 917                                 $gtidSet = $gtidRow ? $gtidRow->Value : '';
 918                         } else {
 919                                 $gtidSet = '';
 920                         }
 921
 922                         return new MySQLMasterPos( $row->File, $row->Position, $gtidSet );
 923                 } else {
 924                         return false;
 925                 }
 926         }
 927
 928         public function serverIsReadOnly() {
 929                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'read_only'", __METHOD__ );
 930                 $row = $this->fetchObject( $res );
 931
 932                 return $row ? ( strtolower( $row->Value ) === 'on' ) : false;
 933         }
 934
 935         /**
 936          * @param string $index
 937          * @return string
 938          */
 939         function useIndexClause( $index ) {
 940                 return "FORCE INDEX (" . $this->indexName( $index ) . ")";
 941         }
 942
 943         /**
 944          * @param string $index
 945          * @return string
 946          */
 947         function ignoreIndexClause( $index ) {
 948                 return "IGNORE INDEX (" . $this->indexName( $index ) . ")";
 949         }
 950
 951         /**
 952          * @return string
 953          */
 954         function lowPriorityOption() {
 955                 return 'LOW_PRIORITY';
 956         }
 957
 958         /**
 959          * @return string
 960          */
 961         public function getSoftwareLink() {
 962                 // MariaDB includes its name in its version string; this is how MariaDB's version of
 963                 // the mysql command-line client identifies MariaDB servers (see mariadb_connection()
 964                 // in libmysql/libmysql.c).
 965                 $version = $this->getServerVersion();
 966                 if ( strpos( $version, 'MariaDB' ) !== false || strpos( $version, '-maria-' ) !== false ) {
 967                         return '[{{int:version-db-mariadb-url}} MariaDB]';
 968                 }
 969
 970                 // Percona Server's version suffix is not very distinctive, and @@version_comment
 971                 // doesn't give the necessary info for source builds, so assume the server is MySQL.
 972                 // (Even Percona's version of mysql doesn't try to make the distinction.)
 973                 return '[{{int:version-db-mysql-url}} MySQL]';
 974         }
 975
 976         /**
 977          * @return string
 978          */
 979         public function getServerVersion() {
 980                 // Not using mysql_get_server_info() or similar for consistency: in the handshake,
 981                 // MariaDB 10 adds the prefix "5.5.5-", and only some newer client libraries strip
 982                 // it off (see RPL_VERSION_HACK in include/mysql_com.h).
 983                 if ( $this->serverVersion === null ) {
 984                         $this->serverVersion = $this->selectField( '', 'VERSION()', '', __METHOD__ );
 985                 }
 986                 return $this->serverVersion;
 987         }
 988
 989         /**
 990          * @param array $options
 991          */
 992         public function setSessionOptions( array $options ) {
 993                 if ( isset( $options['connTimeout'] ) ) {
 994                         $timeout = (int)$options['connTimeout'];
 995                         $this->query( "SET net_read_timeout=$timeout" );
 996                         $this->query( "SET net_write_timeout=$timeout" );
 997                 }
 998         }
 999
1000         /**
1001          * @param string &$sql
1002          * @param string &$newLine
1003          * @return bool
1004          */
1005         public function streamStatementEnd( &$sql, &$newLine ) {
1006                 if ( strtoupper( substr( $newLine, 0, 9 ) ) == 'DELIMITER' ) {
1007                         preg_match( '/^DELIMITER\s+(\S+)/', $newLine, $m );
1008                         $this->delimiter = $m[1];
1009                         $newLine = '';
1010                 }
1011
1012                 return parent::streamStatementEnd( $sql, $newLine );
1013         }
1014
1015         /**
1016          * Check to see if a named lock is available. This is non-blocking.
1017          *
1018          * @param string $lockName Name of lock to poll
1019          * @param string $method Name of method calling us
1020          * @return bool
1021          * @since 1.20
1022          */
1023         public function lockIsFree( $lockName, $method ) {
1024                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1025                 $result = $this->query( "SELECT IS_FREE_LOCK($encName) AS lockstatus", $method );
1026                 $row = $this->fetchObject( $result );
1027
1028                 return ( $row->lockstatus == 1 );
1029         }
1030
1031         /**
1032          * @param string $lockName
1033          * @param string $method
1034          * @param int $timeout
1035          * @return bool
1036          */
1037         public function lock( $lockName, $method, $timeout = 5 ) {
1038                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1039                 $result = $this->query( "SELECT GET_LOCK($encName, $timeout) AS lockstatus", $method );
1040                 $row = $this->fetchObject( $result );
1041
1042                 if ( $row->lockstatus == 1 ) {
1043                         parent::lock( $lockName, $method, $timeout ); // record
1044                         return true;
1045                 }
1046
1047                 $this->queryLogger->warning( __METHOD__ . " failed to acquire lock '$lockName'\n" );
1048
1049                 return false;
1050         }
1051
1052         /**
1053          * FROM MYSQL DOCS:
1054          * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
1055          * @param string $lockName
1056          * @param string $method
1057          * @return bool
1058          */
1059         public function unlock( $lockName, $method ) {
1060                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1061                 $result = $this->query( "SELECT RELEASE_LOCK($encName) as lockstatus", $method );
1062                 $row = $this->fetchObject( $result );
1063
1064                 if ( $row->lockstatus == 1 ) {
1065                         parent::unlock( $lockName, $method ); // record
1066                         return true;
1067                 }
1068
1069                 $this->queryLogger->warning( __METHOD__ . " failed to release lock '$lockName'\n" );
1070
1071                 return false;
1072         }
1073
1074         private function makeLockName( $lockName ) {
1075                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1076                 // Newer version enforce a 64 char length limit.
1077                 return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
1078         }
1079
1080         public function namedLocksEnqueue() {
1081                 return true;
1082         }
1083
1084         public function tableLocksHaveTransactionScope() {
1085                 return false; // tied to TCP connection
1086         }
1087
1088         protected function doLockTables( array $read, array $write, $method ) {
1089                 $items = [];
1090                 foreach ( $write as $table ) {
1091                         $items[] = $this->tableName( $table ) . ' WRITE';
1092                 }
1093                 foreach ( $read as $table ) {
1094                         $items[] = $this->tableName( $table ) . ' READ';
1095                 }
1096
1097                 $sql = "LOCK TABLES " . implode( ',', $items );
1098                 $this->query( $sql, $method );
1099
1100                 return true;
1101         }
1102
1103         protected function doUnlockTables( $method ) {
1104                 $this->query( "UNLOCK TABLES", $method );
1105
1106                 return true;
1107         }
1108
1109         /**
1110          * @param bool $value
1111          */
1112         public function setBigSelects( $value = true ) {
1113                 if ( $value === 'default' ) {
1114                         if ( $this->mDefaultBigSelects === null ) {
1115                                 # Function hasn't been called before so it must already be set to the default
1116                                 return;
1117                         } else {
1118                                 $value = $this->mDefaultBigSelects;
1119                         }
1120                 } elseif ( $this->mDefaultBigSelects === null ) {
1121                         $this->mDefaultBigSelects =
1122                                 (bool)$this->selectField( false, '@@sql_big_selects', '', __METHOD__ );
1123                 }
1124                 $encValue = $value ? '1' : '0';
1125                 $this->query( "SET sql_big_selects=$encValue", __METHOD__ );
1126         }
1127
1128         /**
1129          * DELETE where the condition is a join. MySql uses multi-table deletes.
1130          * @param string $delTable
1131          * @param string $joinTable
1132          * @param string $delVar
1133          * @param string $joinVar
1134          * @param array|string $conds
1135          * @param bool|string $fname
1136          * @throws DBUnexpectedError
1137          * @return bool|ResultWrapper
1138          */
1139         public function deleteJoin(
1140                 $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = __METHOD__
1141         ) {
1142                 if ( !$conds ) {
1143                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
1144                 }
1145
1146                 $delTable = $this->tableName( $delTable );
1147                 $joinTable = $this->tableName( $joinTable );
1148                 $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
1149
1150                 if ( $conds != '*' ) {
1151                         $sql .= ' AND ' . $this->makeList( $conds, self::LIST_AND );
1152                 }
1153
1154                 return $this->query( $sql, $fname );
1155         }
1156
1157         /**
1158          * @param string $table
1159          * @param array $rows
1160          * @param array $uniqueIndexes
1161          * @param array $set
1162          * @param string $fname
1163          * @return bool
1164          */
1165         public function upsert( $table, array $rows, array $uniqueIndexes,
1166                 array $set, $fname = __METHOD__
1167         ) {
1168                 if ( !count( $rows ) ) {
1169                         return true; // nothing to do
1170                 }
1171
1172                 if ( !is_array( reset( $rows ) ) ) {
1173                         $rows = [ $rows ];
1174                 }
1175
1176                 $table = $this->tableName( $table );
1177                 $columns = array_keys( $rows[0] );
1178
1179                 $sql = "INSERT INTO $table (" . implode( ',', $columns ) . ') VALUES ';
1180                 $rowTuples = [];
1181                 foreach ( $rows as $row ) {
1182                         $rowTuples[] = '(' . $this->makeList( $row ) . ')';
1183                 }
1184                 $sql .= implode( ',', $rowTuples );
1185                 $sql .= " ON DUPLICATE KEY UPDATE " . $this->makeList( $set, self::LIST_SET );
1186
1187                 return (bool)$this->query( $sql, $fname );
1188         }
1189
1190         /**
1191          * Determines how long the server has been up
1192          *
1193          * @return int
1194          */
1195         public function getServerUptime() {
1196                 $vars = $this->getMysqlStatus( 'Uptime' );
1197
1198                 return (int)$vars['Uptime'];
1199         }
1200
1201         /**
1202          * Determines if the last failure was due to a deadlock
1203          *
1204          * @return bool
1205          */
1206         public function wasDeadlock() {
1207                 return $this->lastErrno() == 1213;
1208         }
1209
1210         /**
1211          * Determines if the last failure was due to a lock timeout
1212          *
1213          * @return bool
1214          */
1215         public function wasLockTimeout() {
1216                 return $this->lastErrno() == 1205;
1217         }
1218
1219         public function wasErrorReissuable() {
1220                 return $this->lastErrno() == 2013 || $this->lastErrno() == 2006;
1221         }
1222
1223         /**
1224          * Determines if the last failure was due to the database being read-only.
1225          *
1226          * @return bool
1227          */
1228         public function wasReadOnlyError() {
1229                 return $this->lastErrno() == 1223 ||
1230                         ( $this->lastErrno() == 1290 && strpos( $this->lastError(), '--read-only' ) !== false );
1231         }
1232
1233         public function wasConnectionError( $errno ) {
1234                 return $errno == 2013 || $errno == 2006;
1235         }
1236
1237         /**
1238          * @param string $oldName
1239          * @param string $newName
1240          * @param bool $temporary
1241          * @param string $fname
1242          * @return bool
1243          */
1244         public function duplicateTableStructure(
1245                 $oldName, $newName, $temporary = false, $fname = __METHOD__
1246         ) {
1247                 $tmp = $temporary ? 'TEMPORARY ' : '';
1248                 $newName = $this->addIdentifierQuotes( $newName );
1249                 $oldName = $this->addIdentifierQuotes( $oldName );
1250                 $query = "CREATE $tmp TABLE $newName (LIKE $oldName)";
1251
1252                 return $this->query( $query, $fname );
1253         }
1254
1255         /**
1256          * List all tables on the database
1257          *
1258          * @param string $prefix Only show tables with this prefix, e.g. mw_
1259          * @param string $fname Calling function name
1260          * @return array
1261          */
1262         public function listTables( $prefix = null, $fname = __METHOD__ ) {
1263                 $result = $this->query( "SHOW TABLES", $fname );
1264
1265                 $endArray = [];
1266
1267                 foreach ( $result as $table ) {
1268                         $vars = get_object_vars( $table );
1269                         $table = array_pop( $vars );
1270
1271                         if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
1272                                 $endArray[] = $table;
1273                         }
1274                 }
1275
1276                 return $endArray;
1277         }
1278
1279         /**
1280          * @param string $tableName
1281          * @param string $fName
1282          * @return bool|ResultWrapper
1283          */
1284         public function dropTable( $tableName, $fName = __METHOD__ ) {
1285                 if ( !$this->tableExists( $tableName, $fName ) ) {
1286                         return false;
1287                 }
1288
1289                 return $this->query( "DROP TABLE IF EXISTS " . $this->tableName( $tableName ), $fName );
1290         }
1291
1292         /**
1293          * Get status information from SHOW STATUS in an associative array
1294          *
1295          * @param string $which
1296          * @return array
1297          */
1298         private function getMysqlStatus( $which = "%" ) {
1299                 $res = $this->query( "SHOW STATUS LIKE '{$which}'" );
1300                 $status = [];
1301
1302                 foreach ( $res as $row ) {
1303                         $status[$row->Variable_name] = $row->Value;
1304                 }
1305
1306                 return $status;
1307         }
1308
1309         /**
1310          * Lists VIEWs in the database
1311          *
1312          * @param string $prefix Only show VIEWs with this prefix, eg.
1313          * unit_test_, or $wgDBprefix. Default: null, would return all views.
1314          * @param string $fname Name of calling function
1315          * @return array
1316          * @since 1.22
1317          */
1318         public function listViews( $prefix = null, $fname = __METHOD__ ) {
1319                 // The name of the column containing the name of the VIEW
1320                 $propertyName = 'Tables_in_' . $this->mDBname;
1321
1322                 // Query for the VIEWS
1323                 $res = $this->query( 'SHOW FULL TABLES WHERE TABLE_TYPE = "VIEW"' );
1324                 $allViews = [];
1325                 foreach ( $res as $row ) {
1326                         array_push( $allViews, $row->$propertyName );
1327                 }
1328
1329                 if ( is_null( $prefix ) || $prefix === '' ) {
1330                         return $allViews;
1331                 }
1332
1333                 $filteredViews = [];
1334                 foreach ( $allViews as $viewName ) {
1335                         // Does the name of this VIEW start with the table-prefix?
1336                         if ( strpos( $viewName, $prefix ) === 0 ) {
1337                                 array_push( $filteredViews, $viewName );
1338                         }
1339                 }
1340
1341                 return $filteredViews;
1342         }
1343
1344         /**
1345          * Differentiates between a TABLE and a VIEW.
1346          *
1347          * @param string $name Name of the TABLE/VIEW to test
1348          * @param string $prefix
1349          * @return bool
1350          * @since 1.22
1351          */
1352         public function isView( $name, $prefix = null ) {
1353                 return in_array( $name, $this->listViews( $prefix ) );
1354         }
1355
1356         /**
1357          * Allows for index remapping in queries where this is not consistent across DBMS
1358          *
1359          * @param string $index
1360          * @return string
1361          */
1362         protected function indexName( $index ) {
1363                 /**
1364                  * When SQLite indexes were introduced in r45764, it was noted that
1365                  * SQLite requires index names to be unique within the whole database,
1366                  * not just within a schema. As discussed in CR r45819, to avoid the
1367                  * need for a schema change on existing installations, the indexes
1368                  * were implicitly mapped from the new names to the old names.
1369                  *
1370                  * This mapping can be removed if DB patches are introduced to alter
1371                  * the relevant tables in existing installations. Note that because
1372                  * this index mapping applies to table creation, even new installations
1373                  * of MySQL have the old names (except for installations created during
1374                  * a period where this mapping was inappropriately removed, see
1375                  * T154872).
1376                  */
1377                 $renamed = [
1378                         'ar_usertext_timestamp' => 'usertext_timestamp',
1379                         'un_user_id' => 'user_id',
1380                         'un_user_ip' => 'user_ip',
1381                 ];
1382
1383                 if ( isset( $renamed[$index] ) ) {
1384                         return $renamed[$index];
1385                 } else {
1386                         return $index;
1387                 }
1388         }
1389 }
1390
1391 class_alias( DatabaseMysqlBase::class, 'DatabaseMysqlBase' );