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 Wikimedia;
  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         /** @var bool|null */
  64         protected $defaultBigSelects = null;
  65
  66         /** @var string|null */
  67         private $serverVersion = null;
  68         /** @var bool|null */
  69         private $insertSelectIsSafe = null;
  70         /** @var stdClass|null */
  71         private $replicationInfoRow = null;
  72
  73         /**
  74          * Additional $params include:
  75          *   - lagDetectionMethod : set to one of (Seconds_Behind_Master,pt-heartbeat).
  76          *       pt-heartbeat assumes the table is at heartbeat.heartbeat
  77          *       and uses UTC timestamps in the heartbeat.ts column.
  78          *       (https://www.percona.com/doc/percona-toolkit/2.2/pt-heartbeat.html)
  79          *   - lagDetectionOptions : if using pt-heartbeat, this can be set to an array map to change
  80          *       the default behavior. Normally, the heartbeat row with the server
  81          *       ID of this server's master will be used. Set the "conds" field to
  82          *       override the query conditions, e.g. ['shard' => 's1'].
  83          *   - useGTIDs : use GTID methods like MASTER_GTID_WAIT() when possible.
  84          *   - insertSelectIsSafe : force that native INSERT SELECT is or is not safe [default: null]
  85          *   - sslKeyPath : path to key file [default: null]
  86          *   - sslCertPath : path to certificate file [default: null]
  87          *   - sslCAFile: path to a single certificate authority PEM file [default: null]
  88          *   - sslCAPath : parth to certificate authority PEM directory [default: null]
  89          *   - sslCiphers : array list of allowable ciphers [default: null]
  90          * @param array $params
  91          */
  92         function __construct( array $params ) {
  93                 $this->lagDetectionMethod = isset( $params['lagDetectionMethod'] )
  94                         ? $params['lagDetectionMethod']
  95                         : 'Seconds_Behind_Master';
  96                 $this->lagDetectionOptions = isset( $params['lagDetectionOptions'] )
  97                         ? $params['lagDetectionOptions']
  98                         : [];
  99                 $this->useGTIDs = !empty( $params['useGTIDs' ] );
 100                 foreach ( [ 'KeyPath', 'CertPath', 'CAFile', 'CAPath', 'Ciphers' ] as $name ) {
 101                         $var = "ssl{$name}";
 102                         if ( isset( $params[$var] ) ) {
 103                                 $this->$var = $params[$var];
 104                         }
 105                 }
 106                 $this->sqlMode = isset( $params['sqlMode'] ) ? $params['sqlMode'] : '';
 107                 $this->utf8Mode = !empty( $params['utf8Mode'] );
 108                 $this->insertSelectIsSafe = isset( $params['insertSelectIsSafe'] )
 109                         ? (bool)$params['insertSelectIsSafe'] : null;
 110
 111                 parent::__construct( $params );
 112         }
 113
 114         /**
 115          * @return string
 116          */
 117         public function getType() {
 118                 return 'mysql';
 119         }
 120
 121         /**
 122          * @param string $server
 123          * @param string $user
 124          * @param string $password
 125          * @param string $dbName
 126          * @throws Exception|DBConnectionError
 127          * @return bool
 128          */
 129         public function open( $server, $user, $password, $dbName ) {
 130                 # Close/unset connection handle
 131                 $this->close();
 132
 133                 $this->server = $server;
 134                 $this->user = $user;
 135                 $this->password = $password;
 136                 $this->dbName = $dbName;
 137
 138                 $this->installErrorHandler();
 139                 try {
 140                         $this->conn = $this->mysqlConnect( $this->server );
 141                 } catch ( Exception $ex ) {
 142                         $this->restoreErrorHandler();
 143                         throw $ex;
 144                 }
 145                 $error = $this->restoreErrorHandler();
 146
 147                 # Always log connection errors
 148                 if ( !$this->conn ) {
 149                         if ( !$error ) {
 150                                 $error = $this->lastError();
 151                         }
 152                         $this->connLogger->error(
 153                                 "Error connecting to {db_server}: {error}",
 154                                 $this->getLogContext( [
 155                                         'method' => __METHOD__,
 156                                         'error' => $error,
 157                                 ] )
 158                         );
 159                         $this->connLogger->debug( "DB connection error\n" .
 160                                 "Server: $server, User: $user, Password: " .
 161                                 substr( $password, 0, 3 ) . "..., error: " . $error . "\n" );
 162
 163                         $this->reportConnectionError( $error );
 164                 }
 165
 166                 if ( strlen( $dbName ) ) {
 167                         Wikimedia\suppressWarnings();
 168                         $success = $this->selectDB( $dbName );
 169                         Wikimedia\restoreWarnings();
 170                         if ( !$success ) {
 171                                 $this->queryLogger->error(
 172                                         "Error selecting database {db_name} on server {db_server}",
 173                                         $this->getLogContext( [
 174                                                 'method' => __METHOD__,
 175                                         ] )
 176                                 );
 177                                 $this->queryLogger->debug(
 178                                         "Error selecting database $dbName on server {$this->server}" );
 179
 180                                 $this->reportConnectionError( "Error selecting database $dbName" );
 181                         }
 182                 }
 183
 184                 // Tell the server what we're communicating with
 185                 if ( !$this->connectInitCharset() ) {
 186                         $this->reportConnectionError( "Error setting character set" );
 187                 }
 188
 189                 // Abstract over any insane MySQL defaults
 190                 $set = [ 'group_concat_max_len = 262144' ];
 191                 // Set SQL mode, default is turning them all off, can be overridden or skipped with null
 192                 if ( is_string( $this->sqlMode ) ) {
 193                         $set[] = 'sql_mode = ' . $this->addQuotes( $this->sqlMode );
 194                 }
 195                 // Set any custom settings defined by site config
 196                 // (e.g. https://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html)
 197                 foreach ( $this->sessionVars as $var => $val ) {
 198                         // Escape strings but not numbers to avoid MySQL complaining
 199                         if ( !is_int( $val ) && !is_float( $val ) ) {
 200                                 $val = $this->addQuotes( $val );
 201                         }
 202                         $set[] = $this->addIdentifierQuotes( $var ) . ' = ' . $val;
 203                 }
 204
 205                 if ( $set ) {
 206                         // Use doQuery() to avoid opening implicit transactions (DBO_TRX)
 207                         $success = $this->doQuery( 'SET ' . implode( ', ', $set ) );
 208                         if ( !$success ) {
 209                                 $this->queryLogger->error(
 210                                         'Error setting MySQL variables on server {db_server} (check $wgSQLMode)',
 211                                         $this->getLogContext( [
 212                                                 'method' => __METHOD__,
 213                                         ] )
 214                                 );
 215                                 $this->reportConnectionError(
 216                                         'Error setting MySQL variables on server {db_server} (check $wgSQLMode)' );
 217                         }
 218                 }
 219
 220                 $this->opened = true;
 221
 222                 return true;
 223         }
 224
 225         /**
 226          * Set the character set information right after connection
 227          * @return bool
 228          */
 229         protected function connectInitCharset() {
 230                 if ( $this->utf8Mode ) {
 231                         // Tell the server we're communicating with it in UTF-8.
 232                         // This may engage various charset conversions.
 233                         return $this->mysqlSetCharset( 'utf8' );
 234                 } else {
 235                         return $this->mysqlSetCharset( 'binary' );
 236                 }
 237         }
 238
 239         /**
 240          * Open a connection to a MySQL server
 241          *
 242          * @param string $realServer
 243          * @return mixed Raw connection
 244          * @throws DBConnectionError
 245          */
 246         abstract protected function mysqlConnect( $realServer );
 247
 248         /**
 249          * Set the character set of the MySQL link
 250          *
 251          * @param string $charset
 252          * @return bool
 253          */
 254         abstract protected function mysqlSetCharset( $charset );
 255
 256         /**
 257          * @param ResultWrapper|resource $res
 258          * @throws DBUnexpectedError
 259          */
 260         public function freeResult( $res ) {
 261                 if ( $res instanceof ResultWrapper ) {
 262                         $res = $res->result;
 263                 }
 264                 Wikimedia\suppressWarnings();
 265                 $ok = $this->mysqlFreeResult( $res );
 266                 Wikimedia\restoreWarnings();
 267                 if ( !$ok ) {
 268                         throw new DBUnexpectedError( $this, "Unable to free MySQL result" );
 269                 }
 270         }
 271
 272         /**
 273          * Free result memory
 274          *
 275          * @param resource $res Raw result
 276          * @return bool
 277          */
 278         abstract protected function mysqlFreeResult( $res );
 279
 280         /**
 281          * @param ResultWrapper|resource $res
 282          * @return stdClass|bool
 283          * @throws DBUnexpectedError
 284          */
 285         public function fetchObject( $res ) {
 286                 if ( $res instanceof ResultWrapper ) {
 287                         $res = $res->result;
 288                 }
 289                 Wikimedia\suppressWarnings();
 290                 $row = $this->mysqlFetchObject( $res );
 291                 Wikimedia\restoreWarnings();
 292
 293                 $errno = $this->lastErrno();
 294                 // Unfortunately, mysql_fetch_object does not reset the last errno.
 295                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 296                 // these are the only errors mysql_fetch_object can cause.
 297                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 298                 if ( $errno == 2000 || $errno == 2013 ) {
 299                         throw new DBUnexpectedError(
 300                                 $this,
 301                                 'Error in fetchObject(): ' . htmlspecialchars( $this->lastError() )
 302                         );
 303                 }
 304
 305                 return $row;
 306         }
 307
 308         /**
 309          * Fetch a result row as an object
 310          *
 311          * @param resource $res Raw result
 312          * @return stdClass
 313          */
 314         abstract protected function mysqlFetchObject( $res );
 315
 316         /**
 317          * @param ResultWrapper|resource $res
 318          * @return array|bool
 319          * @throws DBUnexpectedError
 320          */
 321         public function fetchRow( $res ) {
 322                 if ( $res instanceof ResultWrapper ) {
 323                         $res = $res->result;
 324                 }
 325                 Wikimedia\suppressWarnings();
 326                 $row = $this->mysqlFetchArray( $res );
 327                 Wikimedia\restoreWarnings();
 328
 329                 $errno = $this->lastErrno();
 330                 // Unfortunately, mysql_fetch_array does not reset the last errno.
 331                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 332                 // these are the only errors mysql_fetch_array can cause.
 333                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 334                 if ( $errno == 2000 || $errno == 2013 ) {
 335                         throw new DBUnexpectedError(
 336                                 $this,
 337                                 'Error in fetchRow(): ' . htmlspecialchars( $this->lastError() )
 338                         );
 339                 }
 340
 341                 return $row;
 342         }
 343
 344         /**
 345          * Fetch a result row as an associative and numeric array
 346          *
 347          * @param resource $res Raw result
 348          * @return array
 349          */
 350         abstract protected function mysqlFetchArray( $res );
 351
 352         /**
 353          * @throws DBUnexpectedError
 354          * @param ResultWrapper|resource $res
 355          * @return int
 356          */
 357         function numRows( $res ) {
 358                 if ( $res instanceof ResultWrapper ) {
 359                         $res = $res->result;
 360                 }
 361                 Wikimedia\suppressWarnings();
 362                 $n = $this->mysqlNumRows( $res );
 363                 Wikimedia\restoreWarnings();
 364
 365                 // Unfortunately, mysql_num_rows does not reset the last errno.
 366                 // We are not checking for any errors here, since
 367                 // these are no errors mysql_num_rows can cause.
 368                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 369                 // See https://phabricator.wikimedia.org/T44430
 370                 return $n;
 371         }
 372
 373         /**
 374          * Get number of rows in result
 375          *
 376          * @param resource $res Raw result
 377          * @return int
 378          */
 379         abstract protected function mysqlNumRows( $res );
 380
 381         /**
 382          * @param ResultWrapper|resource $res
 383          * @return int
 384          */
 385         public function numFields( $res ) {
 386                 if ( $res instanceof ResultWrapper ) {
 387                         $res = $res->result;
 388                 }
 389
 390                 return $this->mysqlNumFields( $res );
 391         }
 392
 393         /**
 394          * Get number of fields in result
 395          *
 396          * @param resource $res Raw result
 397          * @return int
 398          */
 399         abstract protected function mysqlNumFields( $res );
 400
 401         /**
 402          * @param ResultWrapper|resource $res
 403          * @param int $n
 404          * @return string
 405          */
 406         public function fieldName( $res, $n ) {
 407                 if ( $res instanceof ResultWrapper ) {
 408                         $res = $res->result;
 409                 }
 410
 411                 return $this->mysqlFieldName( $res, $n );
 412         }
 413
 414         /**
 415          * Get the name of the specified field in a result
 416          *
 417          * @param ResultWrapper|resource $res
 418          * @param int $n
 419          * @return string
 420          */
 421         abstract protected function mysqlFieldName( $res, $n );
 422
 423         /**
 424          * mysql_field_type() wrapper
 425          * @param ResultWrapper|resource $res
 426          * @param int $n
 427          * @return string
 428          */
 429         public function fieldType( $res, $n ) {
 430                 if ( $res instanceof ResultWrapper ) {
 431                         $res = $res->result;
 432                 }
 433
 434                 return $this->mysqlFieldType( $res, $n );
 435         }
 436
 437         /**
 438          * Get the type of the specified field in a result
 439          *
 440          * @param ResultWrapper|resource $res
 441          * @param int $n
 442          * @return string
 443          */
 444         abstract protected function mysqlFieldType( $res, $n );
 445
 446         /**
 447          * @param ResultWrapper|resource $res
 448          * @param int $row
 449          * @return bool
 450          */
 451         public function dataSeek( $res, $row ) {
 452                 if ( $res instanceof ResultWrapper ) {
 453                         $res = $res->result;
 454                 }
 455
 456                 return $this->mysqlDataSeek( $res, $row );
 457         }
 458
 459         /**
 460          * Move internal result pointer
 461          *
 462          * @param ResultWrapper|resource $res
 463          * @param int $row
 464          * @return bool
 465          */
 466         abstract protected function mysqlDataSeek( $res, $row );
 467
 468         /**
 469          * @return string
 470          */
 471         public function lastError() {
 472                 if ( $this->conn ) {
 473                         # Even if it's non-zero, it can still be invalid
 474                         Wikimedia\suppressWarnings();
 475                         $error = $this->mysqlError( $this->conn );
 476                         if ( !$error ) {
 477                                 $error = $this->mysqlError();
 478                         }
 479                         Wikimedia\restoreWarnings();
 480                 } else {
 481                         $error = $this->mysqlError();
 482                 }
 483                 if ( $error ) {
 484                         $error .= ' (' . $this->server . ')';
 485                 }
 486
 487                 return $error;
 488         }
 489
 490         /**
 491          * Returns the text of the error message from previous MySQL operation
 492          *
 493          * @param resource $conn Raw connection
 494          * @return string
 495          */
 496         abstract protected function mysqlError( $conn = null );
 497
 498         protected function wasQueryTimeout( $error, $errno ) {
 499                 return $errno == 2062;
 500         }
 501
 502         /**
 503          * @param string $table
 504          * @param array $uniqueIndexes
 505          * @param array $rows
 506          * @param string $fname
 507          * @return ResultWrapper
 508          */
 509         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
 510                 return $this->nativeReplace( $table, $rows, $fname );
 511         }
 512
 513         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
 514                 $row = $this->getReplicationSafetyInfo();
 515                 // For row-based-replication, the resulting changes will be relayed, not the query
 516                 if ( $row->binlog_format === 'ROW' ) {
 517                         return true;
 518                 }
 519                 // LIMIT requires ORDER BY on a unique key or it is non-deterministic
 520                 if ( isset( $selectOptions['LIMIT'] ) ) {
 521                         return false;
 522                 }
 523                 // In MySQL, an INSERT SELECT is only replication safe with row-based
 524                 // replication or if innodb_autoinc_lock_mode is 0. When those
 525                 // conditions aren't met, use non-native mode.
 526                 // While we could try to determine if the insert is safe anyway by
 527                 // checking if the target table has an auto-increment column that
 528                 // isn't set in $varMap, that seems unlikely to be worth the extra
 529                 // complexity.
 530                 return ( (int)$row->innodb_autoinc_lock_mode === 0 );
 531         }
 532
 533         /**
 534          * @return stdClass Process cached row
 535          */
 536         private function getReplicationSafetyInfo() {
 537                 if ( $this->replicationInfoRow === null ) {
 538                         $this->replicationInfoRow = $this->selectRow(
 539                                 false,
 540                                 [
 541                                         'innodb_autoinc_lock_mode' => '@@innodb_autoinc_lock_mode',
 542                                         'binlog_format' => '@@binlog_format',
 543                                 ],
 544                                 [],
 545                                 __METHOD__
 546                         );
 547                 }
 548
 549                 return $this->replicationInfoRow;
 550         }
 551
 552         /**
 553          * Estimate rows in dataset
 554          * Returns estimated count, based on EXPLAIN output
 555          * Takes same arguments as Database::select()
 556          *
 557          * @param string|array $table
 558          * @param string|array $vars
 559          * @param string|array $conds
 560          * @param string $fname
 561          * @param string|array $options
 562          * @return bool|int
 563          */
 564         public function estimateRowCount( $table, $vars = '*', $conds = '',
 565                 $fname = __METHOD__, $options = []
 566         ) {
 567                 $options['EXPLAIN'] = true;
 568                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 569                 if ( $res === false ) {
 570                         return false;
 571                 }
 572                 if ( !$this->numRows( $res ) ) {
 573                         return 0;
 574                 }
 575
 576                 $rows = 1;
 577                 foreach ( $res as $plan ) {
 578                         $rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
 579                 }
 580
 581                 return (int)$rows;
 582         }
 583
 584         public function tableExists( $table, $fname = __METHOD__ ) {
 585                 // Split database and table into proper variables as Database::tableName() returns
 586                 // shared tables prefixed with their database, which do not work in SHOW TABLES statements
 587                 list( $database, , $prefix, $table ) = $this->qualifiedTableComponents( $table );
 588                 $tableName = "{$prefix}{$table}";
 589
 590                 if ( isset( $this->sessionTempTables[$tableName] ) ) {
 591                         return true; // already known to exist and won't show in SHOW TABLES anyway
 592                 }
 593
 594                 // We can't use buildLike() here, because it specifies an escape character
 595                 // other than the backslash, which is the only one supported by SHOW TABLES
 596                 $encLike = $this->escapeLikeInternal( $tableName, '\\' );
 597
 598                 // If the database has been specified (such as for shared tables), use "FROM"
 599                 if ( $database !== '' ) {
 600                         $encDatabase = $this->addIdentifierQuotes( $database );
 601                         $query = "SHOW TABLES FROM $encDatabase LIKE '$encLike'";
 602                 } else {
 603                         $query = "SHOW TABLES LIKE '$encLike'";
 604                 }
 605
 606                 return $this->query( $query, $fname )->numRows() > 0;
 607         }
 608
 609         /**
 610          * @param string $table
 611          * @param string $field
 612          * @return bool|MySQLField
 613          */
 614         public function fieldInfo( $table, $field ) {
 615                 $table = $this->tableName( $table );
 616                 $res = $this->query( "SELECT * FROM $table LIMIT 1", __METHOD__, true );
 617                 if ( !$res ) {
 618                         return false;
 619                 }
 620                 $n = $this->mysqlNumFields( $res->result );
 621                 for ( $i = 0; $i < $n; $i++ ) {
 622                         $meta = $this->mysqlFetchField( $res->result, $i );
 623                         if ( $field == $meta->name ) {
 624                                 return new MySQLField( $meta );
 625                         }
 626                 }
 627
 628                 return false;
 629         }
 630
 631         /**
 632          * Get column information from a result
 633          *
 634          * @param resource $res Raw result
 635          * @param int $n
 636          * @return stdClass
 637          */
 638         abstract protected function mysqlFetchField( $res, $n );
 639
 640         /**
 641          * Get information about an index into an object
 642          * Returns false if the index does not exist
 643          *
 644          * @param string $table
 645          * @param string $index
 646          * @param string $fname
 647          * @return bool|array|null False or null on failure
 648          */
 649         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 650                 # SHOW INDEX works in MySQL 3.23.58, but SHOW INDEXES does not.
 651                 # SHOW INDEX should work for 3.x and up:
 652                 # https://dev.mysql.com/doc/mysql/en/SHOW_INDEX.html
 653                 $table = $this->tableName( $table );
 654                 $index = $this->indexName( $index );
 655
 656                 $sql = 'SHOW INDEX FROM ' . $table;
 657                 $res = $this->query( $sql, $fname );
 658
 659                 if ( !$res ) {
 660                         return null;
 661                 }
 662
 663                 $result = [];
 664
 665                 foreach ( $res as $row ) {
 666                         if ( $row->Key_name == $index ) {
 667                                 $result[] = $row;
 668                         }
 669                 }
 670
 671                 return $result ?: false;
 672         }
 673
 674         /**
 675          * @param string $s
 676          * @return string
 677          */
 678         public function strencode( $s ) {
 679                 return $this->mysqlRealEscapeString( $s );
 680         }
 681
 682         /**
 683          * @param string $s
 684          * @return mixed
 685          */
 686         abstract protected function mysqlRealEscapeString( $s );
 687
 688         public function addQuotes( $s ) {
 689                 if ( is_bool( $s ) ) {
 690                         // Parent would transform to int, which does not play nice with MySQL type juggling.
 691                         // When searching for an int in a string column, the strings are cast to int, which
 692                         // means false would match any string not starting with a number.
 693                         $s = (string)(int)$s;
 694                 }
 695                 return parent::addQuotes( $s );
 696         }
 697
 698         /**
 699          * MySQL uses `backticks` for identifier quoting instead of the sql standard "double quotes".
 700          *
 701          * @param string $s
 702          * @return string
 703          */
 704         public function addIdentifierQuotes( $s ) {
 705                 // Characters in the range \u0001-\uFFFF are valid in a quoted identifier
 706                 // Remove NUL bytes and escape backticks by doubling
 707                 return '`' . str_replace( [ "\0", '`' ], [ '', '``' ], $s ) . '`';
 708         }
 709
 710         /**
 711          * @param string $name
 712          * @return bool
 713          */
 714         public function isQuotedIdentifier( $name ) {
 715                 return strlen( $name ) && $name[0] == '`' && substr( $name, -1, 1 ) == '`';
 716         }
 717
 718         public function getLag() {
 719                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 720                         return $this->getLagFromPtHeartbeat();
 721                 } else {
 722                         return $this->getLagFromSlaveStatus();
 723                 }
 724         }
 725
 726         /**
 727          * @return string
 728          */
 729         protected function getLagDetectionMethod() {
 730                 return $this->lagDetectionMethod;
 731         }
 732
 733         /**
 734          * @return bool|int
 735          */
 736         protected function getLagFromSlaveStatus() {
 737                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 738                 $row = $res ? $res->fetchObject() : false;
 739                 if ( $row && strval( $row->Seconds_Behind_Master ) !== '' ) {
 740                         return intval( $row->Seconds_Behind_Master );
 741                 }
 742
 743                 return false;
 744         }
 745
 746         /**
 747          * @return bool|float
 748          */
 749         protected function getLagFromPtHeartbeat() {
 750                 $options = $this->lagDetectionOptions;
 751
 752                 if ( isset( $options['conds'] ) ) {
 753                         // Best method for multi-DC setups: use logical channel names
 754                         $data = $this->getHeartbeatData( $options['conds'] );
 755                 } else {
 756                         // Standard method: use master server ID (works with stock pt-heartbeat)
 757                         $masterInfo = $this->getMasterServerInfo();
 758                         if ( !$masterInfo ) {
 759                                 $this->queryLogger->error(
 760                                         "Unable to query master of {db_server} for server ID",
 761                                         $this->getLogContext( [
 762                                                 'method' => __METHOD__
 763                                         ] )
 764                                 );
 765
 766                                 return false; // could not get master server ID
 767                         }
 768
 769                         $conds = [ 'server_id' => intval( $masterInfo['serverId'] ) ];
 770                         $data = $this->getHeartbeatData( $conds );
 771                 }
 772
 773                 list( $time, $nowUnix ) = $data;
 774                 if ( $time !== null ) {
 775                         // @time is in ISO format like "2015-09-25T16:48:10.000510"
 776                         $dateTime = new DateTime( $time, new DateTimeZone( 'UTC' ) );
 777                         $timeUnix = (int)$dateTime->format( 'U' ) + $dateTime->format( 'u' ) / 1e6;
 778
 779                         return max( $nowUnix - $timeUnix, 0.0 );
 780                 }
 781
 782                 $this->queryLogger->error(
 783                         "Unable to find pt-heartbeat row for {db_server}",
 784                         $this->getLogContext( [
 785                                 'method' => __METHOD__
 786                         ] )
 787                 );
 788
 789                 return false;
 790         }
 791
 792         protected function getMasterServerInfo() {
 793                 $cache = $this->srvCache;
 794                 $key = $cache->makeGlobalKey(
 795                         'mysql',
 796                         'master-info',
 797                         // Using one key for all cluster replica DBs is preferable
 798                         $this->getLBInfo( 'clusterMasterHost' ) ?: $this->getServer()
 799                 );
 800
 801                 return $cache->getWithSetCallback(
 802                         $key,
 803                         $cache::TTL_INDEFINITE,
 804                         function () use ( $cache, $key ) {
 805                                 // Get and leave a lock key in place for a short period
 806                                 if ( !$cache->lock( $key, 0, 10 ) ) {
 807                                         return false; // avoid master connection spike slams
 808                                 }
 809
 810                                 $conn = $this->getLazyMasterHandle();
 811                                 if ( !$conn ) {
 812                                         return false; // something is misconfigured
 813                                 }
 814
 815                                 // Connect to and query the master; catch errors to avoid outages
 816                                 try {
 817                                         $res = $conn->query( 'SELECT @@server_id AS id', __METHOD__ );
 818                                         $row = $res ? $res->fetchObject() : false;
 819                                         $id = $row ? (int)$row->id : 0;
 820                                 } catch ( DBError $e ) {
 821                                         $id = 0;
 822                                 }
 823
 824                                 // Cache the ID if it was retrieved
 825                                 return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
 826                         }
 827                 );
 828         }
 829
 830         /**
 831          * @param array $conds WHERE clause conditions to find a row
 832          * @return array (heartbeat `ts` column value or null, UNIX timestamp) for the newest beat
 833          * @see https://www.percona.com/doc/percona-toolkit/2.1/pt-heartbeat.html
 834          */
 835         protected function getHeartbeatData( array $conds ) {
 836                 // Query time and trip time are not counted
 837                 $nowUnix = microtime( true );
 838                 // Do not bother starting implicit transactions here
 839                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
 840                 try {
 841                         $whereSQL = $this->makeList( $conds, self::LIST_AND );
 842                         // Use ORDER BY for channel based queries since that field might not be UNIQUE.
 843                         // Note: this would use "TIMESTAMPDIFF(MICROSECOND,ts,UTC_TIMESTAMP(6))" but the
 844                         // percision field is not supported in MySQL <= 5.5.
 845                         $res = $this->query(
 846                                 "SELECT ts FROM heartbeat.heartbeat WHERE $whereSQL ORDER BY ts DESC LIMIT 1"
 847                         );
 848                         $row = $res ? $res->fetchObject() : false;
 849                 } finally {
 850                         $this->restoreFlags();
 851                 }
 852
 853                 return [ $row ? $row->ts : null, $nowUnix ];
 854         }
 855
 856         protected function getApproximateLagStatus() {
 857                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 858                         // Disable caching since this is fast enough and we don't wan't
 859                         // to be *too* pessimistic by having both the cache TTL and the
 860                         // pt-heartbeat interval count as lag in getSessionLagStatus()
 861                         return parent::getApproximateLagStatus();
 862                 }
 863
 864                 $key = $this->srvCache->makeGlobalKey( 'mysql-lag', $this->getServer() );
 865                 $approxLag = $this->srvCache->get( $key );
 866                 if ( !$approxLag ) {
 867                         $approxLag = parent::getApproximateLagStatus();
 868                         $this->srvCache->set( $key, $approxLag, 1 );
 869                 }
 870
 871                 return $approxLag;
 872         }
 873
 874         public function masterPosWait( DBMasterPos $pos, $timeout ) {
 875                 if ( !( $pos instanceof MySQLMasterPos ) ) {
 876                         throw new InvalidArgumentException( "Position not an instance of MySQLMasterPos" );
 877                 }
 878
 879                 if ( $this->getLBInfo( 'is static' ) === true ) {
 880                         return 0; // this is a copy of a read-only dataset with no master DB
 881                 } elseif ( $this->lastKnownReplicaPos && $this->lastKnownReplicaPos->hasReached( $pos ) ) {
 882                         return 0; // already reached this point for sure
 883                 }
 884
 885                 // Call doQuery() directly, to avoid opening a transaction if DBO_TRX is set
 886                 if ( $pos->getGTIDs() ) {
 887                         // Ignore GTIDs from domains exclusive to the master DB (presumably inactive)
 888                         $rpos = $this->getReplicaPos();
 889                         $gtidsWait = $rpos ? MySQLMasterPos::getCommonDomainGTIDs( $pos, $rpos ) : [];
 890                         if ( !$gtidsWait ) {
 891                                 return -1; // $pos is from the wrong cluster?
 892                         }
 893                         // Wait on the GTID set (MariaDB only)
 894                         $gtidArg = $this->addQuotes( implode( ',', $gtidsWait ) );
 895                         $res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
 896                 } else {
 897                         // Wait on the binlog coordinates
 898                         $encFile = $this->addQuotes( $pos->getLogFile() );
 899                         $encPos = intval( $pos->pos[1] );
 900                         $res = $this->doQuery( "SELECT MASTER_POS_WAIT($encFile, $encPos, $timeout)" );
 901                 }
 902
 903                 $row = $res ? $this->fetchRow( $res ) : false;
 904                 if ( !$row ) {
 905                         throw new DBExpectedError( $this,
 906                                 "MASTER_POS_WAIT() or MASTER_GTID_WAIT() failed: {$this->lastError()}" );
 907                 }
 908
 909                 // Result can be NULL (error), -1 (timeout), or 0+ per the MySQL manual
 910                 $status = ( $row[0] !== null ) ? intval( $row[0] ) : null;
 911                 if ( $status === null ) {
 912                         if ( !$pos->getGTIDs() ) {
 913                                 // T126436: jobs programmed to wait on master positions might be referencing
 914                                 // binlogs with an old master hostname; this makes MASTER_POS_WAIT() return null.
 915                                 // Try to detect this case and treat the replica DB as having reached the given
 916                                 // position (any master switchover already requires that the new master be caught
 917                                 // up before the switch).
 918                                 $replicationPos = $this->getReplicaPos();
 919                                 if ( $replicationPos && !$replicationPos->channelsMatch( $pos ) ) {
 920                                         $this->lastKnownReplicaPos = $replicationPos;
 921                                         $status = 0;
 922                                 }
 923                         }
 924                 } elseif ( $status >= 0 ) {
 925                         // Remember that this position was reached to save queries next time
 926                         $this->lastKnownReplicaPos = $pos;
 927                 }
 928
 929                 return $status;
 930         }
 931
 932         /**
 933          * Get the position of the master from SHOW SLAVE STATUS
 934          *
 935          * @return MySQLMasterPos|bool
 936          */
 937         public function getReplicaPos() {
 938                 $now = microtime( true );
 939
 940                 if ( $this->useGTIDs ) {
 941                         $res = $this->query( "SELECT @@global.gtid_slave_pos AS Value", __METHOD__ );
 942                         $gtidRow = $this->fetchObject( $res );
 943                         if ( $gtidRow && strlen( $gtidRow->Value ) ) {
 944                                 return new MySQLMasterPos( $gtidRow->Value, $now );
 945                         }
 946                 }
 947
 948                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 949                 $row = $this->fetchObject( $res );
 950                 if ( $row && strlen( $row->Relay_Master_Log_File ) ) {
 951                         return new MySQLMasterPos(
 952                                 "{$row->Relay_Master_Log_File}/{$row->Exec_Master_Log_Pos}",
 953                                 $now
 954                         );
 955                 }
 956
 957                 return false;
 958         }
 959
 960         /**
 961          * Get the position of the master from SHOW MASTER STATUS
 962          *
 963          * @return MySQLMasterPos|bool
 964          */
 965         public function getMasterPos() {
 966                 $now = microtime( true );
 967
 968                 if ( $this->useGTIDs ) {
 969                         $res = $this->query( "SELECT @@global.gtid_binlog_pos AS Value", __METHOD__ );
 970                         $gtidRow = $this->fetchObject( $res );
 971                         if ( $gtidRow && strlen( $gtidRow->Value ) ) {
 972                                 return new MySQLMasterPos( $gtidRow->Value, $now );
 973                         }
 974                 }
 975
 976                 $res = $this->query( 'SHOW MASTER STATUS', __METHOD__ );
 977                 $row = $this->fetchObject( $res );
 978                 if ( $row && strlen( $row->File ) ) {
 979                         return new MySQLMasterPos( "{$row->File}/{$row->Position}", $now );
 980                 }
 981
 982                 return false;
 983         }
 984
 985         public function serverIsReadOnly() {
 986                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'read_only'", __METHOD__ );
 987                 $row = $this->fetchObject( $res );
 988
 989                 return $row ? ( strtolower( $row->Value ) === 'on' ) : false;
 990         }
 991
 992         /**
 993          * @param string $index
 994          * @return string
 995          */
 996         function useIndexClause( $index ) {
 997                 return "FORCE INDEX (" . $this->indexName( $index ) . ")";
 998         }
 999
1000         /**
1001          * @param string $index
1002          * @return string
1003          */
1004         function ignoreIndexClause( $index ) {
1005                 return "IGNORE INDEX (" . $this->indexName( $index ) . ")";
1006         }
1007
1008         /**
1009          * @return string
1010          */
1011         function lowPriorityOption() {
1012                 return 'LOW_PRIORITY';
1013         }
1014
1015         /**
1016          * @return string
1017          */
1018         public function getSoftwareLink() {
1019                 // MariaDB includes its name in its version string; this is how MariaDB's version of
1020                 // the mysql command-line client identifies MariaDB servers (see mariadb_connection()
1021                 // in libmysql/libmysql.c).
1022                 $version = $this->getServerVersion();
1023                 if ( strpos( $version, 'MariaDB' ) !== false || strpos( $version, '-maria-' ) !== false ) {
1024                         return '[{{int:version-db-mariadb-url}} MariaDB]';
1025                 }
1026
1027                 // Percona Server's version suffix is not very distinctive, and @@version_comment
1028                 // doesn't give the necessary info for source builds, so assume the server is MySQL.
1029                 // (Even Percona's version of mysql doesn't try to make the distinction.)
1030                 return '[{{int:version-db-mysql-url}} MySQL]';
1031         }
1032
1033         /**
1034          * @return string
1035          */
1036         public function getServerVersion() {
1037                 // Not using mysql_get_server_info() or similar for consistency: in the handshake,
1038                 // MariaDB 10 adds the prefix "5.5.5-", and only some newer client libraries strip
1039                 // it off (see RPL_VERSION_HACK in include/mysql_com.h).
1040                 if ( $this->serverVersion === null ) {
1041                         $this->serverVersion = $this->selectField( '', 'VERSION()', '', __METHOD__ );
1042                 }
1043                 return $this->serverVersion;
1044         }
1045
1046         /**
1047          * @param array $options
1048          */
1049         public function setSessionOptions( array $options ) {
1050                 if ( isset( $options['connTimeout'] ) ) {
1051                         $timeout = (int)$options['connTimeout'];
1052                         $this->query( "SET net_read_timeout=$timeout" );
1053                         $this->query( "SET net_write_timeout=$timeout" );
1054                 }
1055         }
1056
1057         /**
1058          * @param string &$sql
1059          * @param string &$newLine
1060          * @return bool
1061          */
1062         public function streamStatementEnd( &$sql, &$newLine ) {
1063                 if ( strtoupper( substr( $newLine, 0, 9 ) ) == 'DELIMITER' ) {
1064                         preg_match( '/^DELIMITER\s+(\S+)/', $newLine, $m );
1065                         $this->delimiter = $m[1];
1066                         $newLine = '';
1067                 }
1068
1069                 return parent::streamStatementEnd( $sql, $newLine );
1070         }
1071
1072         /**
1073          * Check to see if a named lock is available. This is non-blocking.
1074          *
1075          * @param string $lockName Name of lock to poll
1076          * @param string $method Name of method calling us
1077          * @return bool
1078          * @since 1.20
1079          */
1080         public function lockIsFree( $lockName, $method ) {
1081                 if ( !parent::lockIsFree( $lockName, $method ) ) {
1082                         return false; // already held
1083                 }
1084
1085                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1086                 $result = $this->query( "SELECT IS_FREE_LOCK($encName) AS lockstatus", $method );
1087                 $row = $this->fetchObject( $result );
1088
1089                 return ( $row->lockstatus == 1 );
1090         }
1091
1092         /**
1093          * @param string $lockName
1094          * @param string $method
1095          * @param int $timeout
1096          * @return bool
1097          */
1098         public function lock( $lockName, $method, $timeout = 5 ) {
1099                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1100                 $result = $this->query( "SELECT GET_LOCK($encName, $timeout) AS lockstatus", $method );
1101                 $row = $this->fetchObject( $result );
1102
1103                 if ( $row->lockstatus == 1 ) {
1104                         parent::lock( $lockName, $method, $timeout ); // record
1105                         return true;
1106                 }
1107
1108                 $this->queryLogger->info( __METHOD__ . " failed to acquire lock '{lockname}'",
1109                         [ 'lockname' => $lockName ] );
1110
1111                 return false;
1112         }
1113
1114         /**
1115          * FROM MYSQL DOCS:
1116          * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
1117          * @param string $lockName
1118          * @param string $method
1119          * @return bool
1120          */
1121         public function unlock( $lockName, $method ) {
1122                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1123                 $result = $this->query( "SELECT RELEASE_LOCK($encName) as lockstatus", $method );
1124                 $row = $this->fetchObject( $result );
1125
1126                 if ( $row->lockstatus == 1 ) {
1127                         parent::unlock( $lockName, $method ); // record
1128                         return true;
1129                 }
1130
1131                 $this->queryLogger->warning( __METHOD__ . " failed to release lock '$lockName'\n" );
1132
1133                 return false;
1134         }
1135
1136         private function makeLockName( $lockName ) {
1137                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1138                 // Newer version enforce a 64 char length limit.
1139                 return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
1140         }
1141
1142         public function namedLocksEnqueue() {
1143                 return true;
1144         }
1145
1146         public function tableLocksHaveTransactionScope() {
1147                 return false; // tied to TCP connection
1148         }
1149
1150         protected function doLockTables( array $read, array $write, $method ) {
1151                 $items = [];
1152                 foreach ( $write as $table ) {
1153                         $items[] = $this->tableName( $table ) . ' WRITE';
1154                 }
1155                 foreach ( $read as $table ) {
1156                         $items[] = $this->tableName( $table ) . ' READ';
1157                 }
1158
1159                 $sql = "LOCK TABLES " . implode( ',', $items );
1160                 $this->query( $sql, $method );
1161
1162                 return true;
1163         }
1164
1165         protected function doUnlockTables( $method ) {
1166                 $this->query( "UNLOCK TABLES", $method );
1167
1168                 return true;
1169         }
1170
1171         /**
1172          * @param bool $value
1173          */
1174         public function setBigSelects( $value = true ) {
1175                 if ( $value === 'default' ) {
1176                         if ( $this->defaultBigSelects === null ) {
1177                                 # Function hasn't been called before so it must already be set to the default
1178                                 return;
1179                         } else {
1180                                 $value = $this->defaultBigSelects;
1181                         }
1182                 } elseif ( $this->defaultBigSelects === null ) {
1183                         $this->defaultBigSelects =
1184                                 (bool)$this->selectField( false, '@@sql_big_selects', '', __METHOD__ );
1185                 }
1186                 $encValue = $value ? '1' : '0';
1187                 $this->query( "SET sql_big_selects=$encValue", __METHOD__ );
1188         }
1189
1190         /**
1191          * DELETE where the condition is a join. MySql uses multi-table deletes.
1192          * @param string $delTable
1193          * @param string $joinTable
1194          * @param string $delVar
1195          * @param string $joinVar
1196          * @param array|string $conds
1197          * @param bool|string $fname
1198          * @throws DBUnexpectedError
1199          * @return bool|ResultWrapper
1200          */
1201         public function deleteJoin(
1202                 $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = __METHOD__
1203         ) {
1204                 if ( !$conds ) {
1205                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
1206                 }
1207
1208                 $delTable = $this->tableName( $delTable );
1209                 $joinTable = $this->tableName( $joinTable );
1210                 $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
1211
1212                 if ( $conds != '*' ) {
1213                         $sql .= ' AND ' . $this->makeList( $conds, self::LIST_AND );
1214                 }
1215
1216                 return $this->query( $sql, $fname );
1217         }
1218
1219         /**
1220          * @param string $table
1221          * @param array $rows
1222          * @param array $uniqueIndexes
1223          * @param array $set
1224          * @param string $fname
1225          * @return bool
1226          */
1227         public function upsert( $table, array $rows, array $uniqueIndexes,
1228                 array $set, $fname = __METHOD__
1229         ) {
1230                 if ( !count( $rows ) ) {
1231                         return true; // nothing to do
1232                 }
1233
1234                 if ( !is_array( reset( $rows ) ) ) {
1235                         $rows = [ $rows ];
1236                 }
1237
1238                 $table = $this->tableName( $table );
1239                 $columns = array_keys( $rows[0] );
1240
1241                 $sql = "INSERT INTO $table (" . implode( ',', $columns ) . ') VALUES ';
1242                 $rowTuples = [];
1243                 foreach ( $rows as $row ) {
1244                         $rowTuples[] = '(' . $this->makeList( $row ) . ')';
1245                 }
1246                 $sql .= implode( ',', $rowTuples );
1247                 $sql .= " ON DUPLICATE KEY UPDATE " . $this->makeList( $set, self::LIST_SET );
1248
1249                 return (bool)$this->query( $sql, $fname );
1250         }
1251
1252         /**
1253          * Determines how long the server has been up
1254          *
1255          * @return int
1256          */
1257         public function getServerUptime() {
1258                 $vars = $this->getMysqlStatus( 'Uptime' );
1259
1260                 return (int)$vars['Uptime'];
1261         }
1262
1263         /**
1264          * Determines if the last failure was due to a deadlock
1265          *
1266          * @return bool
1267          */
1268         public function wasDeadlock() {
1269                 return $this->lastErrno() == 1213;
1270         }
1271
1272         /**
1273          * Determines if the last failure was due to a lock timeout
1274          *
1275          * @return bool
1276          */
1277         public function wasLockTimeout() {
1278                 return $this->lastErrno() == 1205;
1279         }
1280
1281         public function wasErrorReissuable() {
1282                 return $this->lastErrno() == 2013 || $this->lastErrno() == 2006;
1283         }
1284
1285         /**
1286          * Determines if the last failure was due to the database being read-only.
1287          *
1288          * @return bool
1289          */
1290         public function wasReadOnlyError() {
1291                 return $this->lastErrno() == 1223 ||
1292                         ( $this->lastErrno() == 1290 && strpos( $this->lastError(), '--read-only' ) !== false );
1293         }
1294
1295         public function wasConnectionError( $errno ) {
1296                 return $errno == 2013 || $errno == 2006;
1297         }
1298
1299         /**
1300          * @param string $oldName
1301          * @param string $newName
1302          * @param bool $temporary
1303          * @param string $fname
1304          * @return bool
1305          */
1306         public function duplicateTableStructure(
1307                 $oldName, $newName, $temporary = false, $fname = __METHOD__
1308         ) {
1309                 $tmp = $temporary ? 'TEMPORARY ' : '';
1310                 $newName = $this->addIdentifierQuotes( $newName );
1311                 $oldName = $this->addIdentifierQuotes( $oldName );
1312                 $query = "CREATE $tmp TABLE $newName (LIKE $oldName)";
1313
1314                 return $this->query( $query, $fname );
1315         }
1316
1317         /**
1318          * List all tables on the database
1319          *
1320          * @param string $prefix Only show tables with this prefix, e.g. mw_
1321          * @param string $fname Calling function name
1322          * @return array
1323          */
1324         public function listTables( $prefix = null, $fname = __METHOD__ ) {
1325                 $result = $this->query( "SHOW TABLES", $fname );
1326
1327                 $endArray = [];
1328
1329                 foreach ( $result as $table ) {
1330                         $vars = get_object_vars( $table );
1331                         $table = array_pop( $vars );
1332
1333                         if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
1334                                 $endArray[] = $table;
1335                         }
1336                 }
1337
1338                 return $endArray;
1339         }
1340
1341         /**
1342          * @param string $tableName
1343          * @param string $fName
1344          * @return bool|ResultWrapper
1345          */
1346         public function dropTable( $tableName, $fName = __METHOD__ ) {
1347                 if ( !$this->tableExists( $tableName, $fName ) ) {
1348                         return false;
1349                 }
1350
1351                 return $this->query( "DROP TABLE IF EXISTS " . $this->tableName( $tableName ), $fName );
1352         }
1353
1354         /**
1355          * Get status information from SHOW STATUS in an associative array
1356          *
1357          * @param string $which
1358          * @return array
1359          */
1360         private function getMysqlStatus( $which = "%" ) {
1361                 $res = $this->query( "SHOW STATUS LIKE '{$which}'" );
1362                 $status = [];
1363
1364                 foreach ( $res as $row ) {
1365                         $status[$row->Variable_name] = $row->Value;
1366                 }
1367
1368                 return $status;
1369         }
1370
1371         /**
1372          * Lists VIEWs in the database
1373          *
1374          * @param string $prefix Only show VIEWs with this prefix, eg.
1375          * unit_test_, or $wgDBprefix. Default: null, would return all views.
1376          * @param string $fname Name of calling function
1377          * @return array
1378          * @since 1.22
1379          */
1380         public function listViews( $prefix = null, $fname = __METHOD__ ) {
1381                 // The name of the column containing the name of the VIEW
1382                 $propertyName = 'Tables_in_' . $this->dbName;
1383
1384                 // Query for the VIEWS
1385                 $res = $this->query( 'SHOW FULL TABLES WHERE TABLE_TYPE = "VIEW"' );
1386                 $allViews = [];
1387                 foreach ( $res as $row ) {
1388                         array_push( $allViews, $row->$propertyName );
1389                 }
1390
1391                 if ( is_null( $prefix ) || $prefix === '' ) {
1392                         return $allViews;
1393                 }
1394
1395                 $filteredViews = [];
1396                 foreach ( $allViews as $viewName ) {
1397                         // Does the name of this VIEW start with the table-prefix?
1398                         if ( strpos( $viewName, $prefix ) === 0 ) {
1399                                 array_push( $filteredViews, $viewName );
1400                         }
1401                 }
1402
1403                 return $filteredViews;
1404         }
1405
1406         /**
1407          * Differentiates between a TABLE and a VIEW.
1408          *
1409          * @param string $name Name of the TABLE/VIEW to test
1410          * @param string $prefix
1411          * @return bool
1412          * @since 1.22
1413          */
1414         public function isView( $name, $prefix = null ) {
1415                 return in_array( $name, $this->listViews( $prefix ) );
1416         }
1417
1418         /**
1419          * Allows for index remapping in queries where this is not consistent across DBMS
1420          *
1421          * @param string $index
1422          * @return string
1423          */
1424         protected function indexName( $index ) {
1425                 /**
1426                  * When SQLite indexes were introduced in r45764, it was noted that
1427                  * SQLite requires index names to be unique within the whole database,
1428                  * not just within a schema. As discussed in CR r45819, to avoid the
1429                  * need for a schema change on existing installations, the indexes
1430                  * were implicitly mapped from the new names to the old names.
1431                  *
1432                  * This mapping can be removed if DB patches are introduced to alter
1433                  * the relevant tables in existing installations. Note that because
1434                  * this index mapping applies to table creation, even new installations
1435                  * of MySQL have the old names (except for installations created during
1436                  * a period where this mapping was inappropriately removed, see
1437                  * T154872).
1438                  */
1439                 $renamed = [
1440                         'ar_usertext_timestamp' => 'usertext_timestamp',
1441                         'un_user_id' => 'user_id',
1442                         'un_user_ip' => 'user_ip',
1443                 ];
1444
1445                 if ( isset( $renamed[$index] ) ) {
1446                         return $renamed[$index];
1447                 } else {
1448                         return $index;
1449                 }
1450         }
1451
1452         protected function isTransactableQuery( $sql ) {
1453                 return parent::isTransactableQuery( $sql ) &&
1454                         !preg_match( '/^SELECT\s+(GET|RELEASE|IS_FREE)_LOCK\(/', $sql );
1455         }
1456 }
1457
1458 class_alias( DatabaseMysqlBase::class, 'DatabaseMysqlBase' );