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         // Cache getServerId() for 24 hours
  74         const SERVER_ID_CACHE_TTL = 86400;
  75
  76         /** @var float Warn if lag estimates are made for transactions older than this many seconds */
  77         const LAG_STALE_WARN_THRESHOLD = 0.100;
  78
  79         /**
  80          * Additional $params include:
  81          *   - lagDetectionMethod : set to one of (Seconds_Behind_Master,pt-heartbeat).
  82          *       pt-heartbeat assumes the table is at heartbeat.heartbeat
  83          *       and uses UTC timestamps in the heartbeat.ts column.
  84          *       (https://www.percona.com/doc/percona-toolkit/2.2/pt-heartbeat.html)
  85          *   - lagDetectionOptions : if using pt-heartbeat, this can be set to an array map to change
  86          *       the default behavior. Normally, the heartbeat row with the server
  87          *       ID of this server's master will be used. Set the "conds" field to
  88          *       override the query conditions, e.g. ['shard' => 's1'].
  89          *   - useGTIDs : use GTID methods like MASTER_GTID_WAIT() when possible.
  90          *   - insertSelectIsSafe : force that native INSERT SELECT is or is not safe [default: null]
  91          *   - sslKeyPath : path to key file [default: null]
  92          *   - sslCertPath : path to certificate file [default: null]
  93          *   - sslCAFile: path to a single certificate authority PEM file [default: null]
  94          *   - sslCAPath : parth to certificate authority PEM directory [default: null]
  95          *   - sslCiphers : array list of allowable ciphers [default: null]
  96          * @param array $params
  97          */
  98         function __construct( array $params ) {
  99                 $this->lagDetectionMethod = isset( $params['lagDetectionMethod'] )
 100                         ? $params['lagDetectionMethod']
 101                         : 'Seconds_Behind_Master';
 102                 $this->lagDetectionOptions = isset( $params['lagDetectionOptions'] )
 103                         ? $params['lagDetectionOptions']
 104                         : [];
 105                 $this->useGTIDs = !empty( $params['useGTIDs' ] );
 106                 foreach ( [ 'KeyPath', 'CertPath', 'CAFile', 'CAPath', 'Ciphers' ] as $name ) {
 107                         $var = "ssl{$name}";
 108                         if ( isset( $params[$var] ) ) {
 109                                 $this->$var = $params[$var];
 110                         }
 111                 }
 112                 $this->sqlMode = isset( $params['sqlMode'] ) ? $params['sqlMode'] : '';
 113                 $this->utf8Mode = !empty( $params['utf8Mode'] );
 114                 $this->insertSelectIsSafe = isset( $params['insertSelectIsSafe'] )
 115                         ? (bool)$params['insertSelectIsSafe'] : null;
 116
 117                 parent::__construct( $params );
 118         }
 119
 120         /**
 121          * @return string
 122          */
 123         public function getType() {
 124                 return 'mysql';
 125         }
 126
 127         /**
 128          * @param string $server
 129          * @param string $user
 130          * @param string $password
 131          * @param string $dbName
 132          * @throws Exception|DBConnectionError
 133          * @return bool
 134          */
 135         public function open( $server, $user, $password, $dbName ) {
 136                 # Close/unset connection handle
 137                 $this->close();
 138
 139                 $this->server = $server;
 140                 $this->user = $user;
 141                 $this->password = $password;
 142                 $this->dbName = $dbName;
 143
 144                 $this->installErrorHandler();
 145                 try {
 146                         $this->conn = $this->mysqlConnect( $this->server );
 147                 } catch ( Exception $ex ) {
 148                         $this->restoreErrorHandler();
 149                         throw $ex;
 150                 }
 151                 $error = $this->restoreErrorHandler();
 152
 153                 # Always log connection errors
 154                 if ( !$this->conn ) {
 155                         $error = $error ?: $this->lastError();
 156                         $this->connLogger->error(
 157                                 "Error connecting to {db_server}: {error}",
 158                                 $this->getLogContext( [
 159                                         'method' => __METHOD__,
 160                                         'error' => $error,
 161                                 ] )
 162                         );
 163                         $this->connLogger->debug( "DB connection error\n" .
 164                                 "Server: $server, User: $user, Password: " .
 165                                 substr( $password, 0, 3 ) . "..., error: " . $error . "\n" );
 166
 167                         throw new DBConnectionError( $this, $error );
 168                 }
 169
 170                 if ( strlen( $dbName ) ) {
 171                         Wikimedia\suppressWarnings();
 172                         $success = $this->selectDB( $dbName );
 173                         Wikimedia\restoreWarnings();
 174                         if ( !$success ) {
 175                                 $error = $this->lastError();
 176                                 $this->queryLogger->error(
 177                                         "Error selecting database {db_name} on server {db_server}: {error}",
 178                                         $this->getLogContext( [
 179                                                 'method' => __METHOD__,
 180                                                 'error' => $error,
 181                                         ] )
 182                                 );
 183                                 throw new DBConnectionError( $this, "Error selecting database $dbName: $error" );
 184                         }
 185                 }
 186
 187                 // Tell the server what we're communicating with
 188                 if ( !$this->connectInitCharset() ) {
 189                         $error = $this->lastError();
 190                         $this->queryLogger->error(
 191                                 "Error setting character set: {error}",
 192                                 $this->getLogContext( [
 193                                         'method' => __METHOD__,
 194                                         'error' => $this->lastError(),
 195                                 ] )
 196                         );
 197                         throw new DBConnectionError( $this, "Error setting character set: $error" );
 198                 }
 199
 200                 // Abstract over any insane MySQL defaults
 201                 $set = [ 'group_concat_max_len = 262144' ];
 202                 // Set SQL mode, default is turning them all off, can be overridden or skipped with null
 203                 if ( is_string( $this->sqlMode ) ) {
 204                         $set[] = 'sql_mode = ' . $this->addQuotes( $this->sqlMode );
 205                 }
 206                 // Set any custom settings defined by site config
 207                 // (e.g. https://dev.mysql.com/doc/refman/4.1/en/innodb-parameters.html)
 208                 foreach ( $this->sessionVars as $var => $val ) {
 209                         // Escape strings but not numbers to avoid MySQL complaining
 210                         if ( !is_int( $val ) && !is_float( $val ) ) {
 211                                 $val = $this->addQuotes( $val );
 212                         }
 213                         $set[] = $this->addIdentifierQuotes( $var ) . ' = ' . $val;
 214                 }
 215
 216                 if ( $set ) {
 217                         // Use doQuery() to avoid opening implicit transactions (DBO_TRX)
 218                         $success = $this->doQuery( 'SET ' . implode( ', ', $set ) );
 219                         if ( !$success ) {
 220                                 $error = $this->lastError();
 221                                 $this->queryLogger->error(
 222                                         'Error setting MySQL variables on server {db_server}: {error}',
 223                                         $this->getLogContext( [
 224                                                 'method' => __METHOD__,
 225                                                 'error' => $error,
 226                                         ] )
 227                                 );
 228                                 throw new DBConnectionError( $this, "Error setting MySQL variables: $error" );
 229                         }
 230                 }
 231
 232                 $this->opened = true;
 233
 234                 return true;
 235         }
 236
 237         /**
 238          * Set the character set information right after connection
 239          * @return bool
 240          */
 241         protected function connectInitCharset() {
 242                 if ( $this->utf8Mode ) {
 243                         // Tell the server we're communicating with it in UTF-8.
 244                         // This may engage various charset conversions.
 245                         return $this->mysqlSetCharset( 'utf8' );
 246                 } else {
 247                         return $this->mysqlSetCharset( 'binary' );
 248                 }
 249         }
 250
 251         /**
 252          * Open a connection to a MySQL server
 253          *
 254          * @param string $realServer
 255          * @return mixed Raw connection
 256          * @throws DBConnectionError
 257          */
 258         abstract protected function mysqlConnect( $realServer );
 259
 260         /**
 261          * Set the character set of the MySQL link
 262          *
 263          * @param string $charset
 264          * @return bool
 265          */
 266         abstract protected function mysqlSetCharset( $charset );
 267
 268         /**
 269          * @param ResultWrapper|resource $res
 270          * @throws DBUnexpectedError
 271          */
 272         public function freeResult( $res ) {
 273                 if ( $res instanceof ResultWrapper ) {
 274                         $res = $res->result;
 275                 }
 276                 Wikimedia\suppressWarnings();
 277                 $ok = $this->mysqlFreeResult( $res );
 278                 Wikimedia\restoreWarnings();
 279                 if ( !$ok ) {
 280                         throw new DBUnexpectedError( $this, "Unable to free MySQL result" );
 281                 }
 282         }
 283
 284         /**
 285          * Free result memory
 286          *
 287          * @param resource $res Raw result
 288          * @return bool
 289          */
 290         abstract protected function mysqlFreeResult( $res );
 291
 292         /**
 293          * @param ResultWrapper|resource $res
 294          * @return stdClass|bool
 295          * @throws DBUnexpectedError
 296          */
 297         public function fetchObject( $res ) {
 298                 if ( $res instanceof ResultWrapper ) {
 299                         $res = $res->result;
 300                 }
 301                 Wikimedia\suppressWarnings();
 302                 $row = $this->mysqlFetchObject( $res );
 303                 Wikimedia\restoreWarnings();
 304
 305                 $errno = $this->lastErrno();
 306                 // Unfortunately, mysql_fetch_object does not reset the last errno.
 307                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 308                 // these are the only errors mysql_fetch_object can cause.
 309                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 310                 if ( $errno == 2000 || $errno == 2013 ) {
 311                         throw new DBUnexpectedError(
 312                                 $this,
 313                                 'Error in fetchObject(): ' . htmlspecialchars( $this->lastError() )
 314                         );
 315                 }
 316
 317                 return $row;
 318         }
 319
 320         /**
 321          * Fetch a result row as an object
 322          *
 323          * @param resource $res Raw result
 324          * @return stdClass
 325          */
 326         abstract protected function mysqlFetchObject( $res );
 327
 328         /**
 329          * @param IResultWrapper|resource $res
 330          * @return array|bool
 331          * @throws DBUnexpectedError
 332          */
 333         public function fetchRow( $res ) {
 334                 if ( $res instanceof ResultWrapper ) {
 335                         $res = $res->result;
 336                 }
 337                 Wikimedia\suppressWarnings();
 338                 $row = $this->mysqlFetchArray( $res );
 339                 Wikimedia\restoreWarnings();
 340
 341                 $errno = $this->lastErrno();
 342                 // Unfortunately, mysql_fetch_array does not reset the last errno.
 343                 // Only check for CR_SERVER_LOST and CR_UNKNOWN_ERROR, as
 344                 // these are the only errors mysql_fetch_array can cause.
 345                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 346                 if ( $errno == 2000 || $errno == 2013 ) {
 347                         throw new DBUnexpectedError(
 348                                 $this,
 349                                 'Error in fetchRow(): ' . htmlspecialchars( $this->lastError() )
 350                         );
 351                 }
 352
 353                 return $row;
 354         }
 355
 356         /**
 357          * Fetch a result row as an associative and numeric array
 358          *
 359          * @param resource $res Raw result
 360          * @return array
 361          */
 362         abstract protected function mysqlFetchArray( $res );
 363
 364         /**
 365          * @throws DBUnexpectedError
 366          * @param ResultWrapper|resource $res
 367          * @return int
 368          */
 369         function numRows( $res ) {
 370                 if ( $res instanceof ResultWrapper ) {
 371                         $res = $res->result;
 372                 }
 373                 Wikimedia\suppressWarnings();
 374                 $n = $this->mysqlNumRows( $res );
 375                 Wikimedia\restoreWarnings();
 376
 377                 // Unfortunately, mysql_num_rows does not reset the last errno.
 378                 // We are not checking for any errors here, since
 379                 // these are no errors mysql_num_rows can cause.
 380                 // See https://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html.
 381                 // See https://phabricator.wikimedia.org/T44430
 382                 return $n;
 383         }
 384
 385         /**
 386          * Get number of rows in result
 387          *
 388          * @param resource $res Raw result
 389          * @return int
 390          */
 391         abstract protected function mysqlNumRows( $res );
 392
 393         /**
 394          * @param ResultWrapper|resource $res
 395          * @return int
 396          */
 397         public function numFields( $res ) {
 398                 if ( $res instanceof ResultWrapper ) {
 399                         $res = $res->result;
 400                 }
 401
 402                 return $this->mysqlNumFields( $res );
 403         }
 404
 405         /**
 406          * Get number of fields in result
 407          *
 408          * @param resource $res Raw result
 409          * @return int
 410          */
 411         abstract protected function mysqlNumFields( $res );
 412
 413         /**
 414          * @param ResultWrapper|resource $res
 415          * @param int $n
 416          * @return string
 417          */
 418         public function fieldName( $res, $n ) {
 419                 if ( $res instanceof ResultWrapper ) {
 420                         $res = $res->result;
 421                 }
 422
 423                 return $this->mysqlFieldName( $res, $n );
 424         }
 425
 426         /**
 427          * Get the name of the specified field in a result
 428          *
 429          * @param ResultWrapper|resource $res
 430          * @param int $n
 431          * @return string
 432          */
 433         abstract protected function mysqlFieldName( $res, $n );
 434
 435         /**
 436          * mysql_field_type() wrapper
 437          * @param ResultWrapper|resource $res
 438          * @param int $n
 439          * @return string
 440          */
 441         public function fieldType( $res, $n ) {
 442                 if ( $res instanceof ResultWrapper ) {
 443                         $res = $res->result;
 444                 }
 445
 446                 return $this->mysqlFieldType( $res, $n );
 447         }
 448
 449         /**
 450          * Get the type of the specified field in a result
 451          *
 452          * @param ResultWrapper|resource $res
 453          * @param int $n
 454          * @return string
 455          */
 456         abstract protected function mysqlFieldType( $res, $n );
 457
 458         /**
 459          * @param ResultWrapper|resource $res
 460          * @param int $row
 461          * @return bool
 462          */
 463         public function dataSeek( $res, $row ) {
 464                 if ( $res instanceof ResultWrapper ) {
 465                         $res = $res->result;
 466                 }
 467
 468                 return $this->mysqlDataSeek( $res, $row );
 469         }
 470
 471         /**
 472          * Move internal result pointer
 473          *
 474          * @param ResultWrapper|resource $res
 475          * @param int $row
 476          * @return bool
 477          */
 478         abstract protected function mysqlDataSeek( $res, $row );
 479
 480         /**
 481          * @return string
 482          */
 483         public function lastError() {
 484                 if ( $this->conn ) {
 485                         # Even if it's non-zero, it can still be invalid
 486                         Wikimedia\suppressWarnings();
 487                         $error = $this->mysqlError( $this->conn );
 488                         if ( !$error ) {
 489                                 $error = $this->mysqlError();
 490                         }
 491                         Wikimedia\restoreWarnings();
 492                 } else {
 493                         $error = $this->mysqlError();
 494                 }
 495                 if ( $error ) {
 496                         $error .= ' (' . $this->server . ')';
 497                 }
 498
 499                 return $error;
 500         }
 501
 502         /**
 503          * Returns the text of the error message from previous MySQL operation
 504          *
 505          * @param resource $conn Raw connection
 506          * @return string
 507          */
 508         abstract protected function mysqlError( $conn = null );
 509
 510         protected function wasQueryTimeout( $error, $errno ) {
 511                 return $errno == 2062;
 512         }
 513
 514         /**
 515          * @param string $table
 516          * @param array $uniqueIndexes
 517          * @param array $rows
 518          * @param string $fname
 519          * @return ResultWrapper
 520          */
 521         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
 522                 return $this->nativeReplace( $table, $rows, $fname );
 523         }
 524
 525         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
 526                 $row = $this->getReplicationSafetyInfo();
 527                 // For row-based-replication, the resulting changes will be relayed, not the query
 528                 if ( $row->binlog_format === 'ROW' ) {
 529                         return true;
 530                 }
 531                 // LIMIT requires ORDER BY on a unique key or it is non-deterministic
 532                 if ( isset( $selectOptions['LIMIT'] ) ) {
 533                         return false;
 534                 }
 535                 // In MySQL, an INSERT SELECT is only replication safe with row-based
 536                 // replication or if innodb_autoinc_lock_mode is 0. When those
 537                 // conditions aren't met, use non-native mode.
 538                 // While we could try to determine if the insert is safe anyway by
 539                 // checking if the target table has an auto-increment column that
 540                 // isn't set in $varMap, that seems unlikely to be worth the extra
 541                 // complexity.
 542                 return (
 543                         in_array( 'NO_AUTO_COLUMNS', $insertOptions ) ||
 544                         (int)$row->innodb_autoinc_lock_mode === 0
 545                 );
 546         }
 547
 548         /**
 549          * @return stdClass Process cached row
 550          */
 551         protected function getReplicationSafetyInfo() {
 552                 if ( $this->replicationInfoRow === null ) {
 553                         $this->replicationInfoRow = $this->selectRow(
 554                                 false,
 555                                 [
 556                                         'innodb_autoinc_lock_mode' => '@@innodb_autoinc_lock_mode',
 557                                         'binlog_format' => '@@binlog_format',
 558                                 ],
 559                                 [],
 560                                 __METHOD__
 561                         );
 562                 }
 563
 564                 return $this->replicationInfoRow;
 565         }
 566
 567         /**
 568          * Estimate rows in dataset
 569          * Returns estimated count, based on EXPLAIN output
 570          * Takes same arguments as Database::select()
 571          *
 572          * @param string|array $table
 573          * @param string|array $var
 574          * @param string|array $conds
 575          * @param string $fname
 576          * @param string|array $options
 577          * @param array $join_conds
 578          * @return bool|int
 579          */
 580         public function estimateRowCount( $table, $var = '*', $conds = '',
 581                 $fname = __METHOD__, $options = [], $join_conds = []
 582         ) {
 583                 $conds = $this->normalizeConditions( $conds, $fname );
 584                 $column = $this->extractSingleFieldFromList( $var );
 585                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
 586                         $conds[] = "$column IS NOT NULL";
 587                 }
 588
 589                 $options['EXPLAIN'] = true;
 590                 $res = $this->select( $table, $var, $conds, $fname, $options, $join_conds );
 591                 if ( $res === false ) {
 592                         return false;
 593                 }
 594                 if ( !$this->numRows( $res ) ) {
 595                         return 0;
 596                 }
 597
 598                 $rows = 1;
 599                 foreach ( $res as $plan ) {
 600                         $rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
 601                 }
 602
 603                 return (int)$rows;
 604         }
 605
 606         public function tableExists( $table, $fname = __METHOD__ ) {
 607                 // Split database and table into proper variables as Database::tableName() returns
 608                 // shared tables prefixed with their database, which do not work in SHOW TABLES statements
 609                 list( $database, , $prefix, $table ) = $this->qualifiedTableComponents( $table );
 610                 $tableName = "{$prefix}{$table}";
 611
 612                 if ( isset( $this->sessionTempTables[$tableName] ) ) {
 613                         return true; // already known to exist and won't show in SHOW TABLES anyway
 614                 }
 615
 616                 // We can't use buildLike() here, because it specifies an escape character
 617                 // other than the backslash, which is the only one supported by SHOW TABLES
 618                 $encLike = $this->escapeLikeInternal( $tableName, '\\' );
 619
 620                 // If the database has been specified (such as for shared tables), use "FROM"
 621                 if ( $database !== '' ) {
 622                         $encDatabase = $this->addIdentifierQuotes( $database );
 623                         $query = "SHOW TABLES FROM $encDatabase LIKE '$encLike'";
 624                 } else {
 625                         $query = "SHOW TABLES LIKE '$encLike'";
 626                 }
 627
 628                 return $this->query( $query, $fname )->numRows() > 0;
 629         }
 630
 631         /**
 632          * @param string $table
 633          * @param string $field
 634          * @return bool|MySQLField
 635          */
 636         public function fieldInfo( $table, $field ) {
 637                 $table = $this->tableName( $table );
 638                 $res = $this->query( "SELECT * FROM $table LIMIT 1", __METHOD__, true );
 639                 if ( !$res ) {
 640                         return false;
 641                 }
 642                 $n = $this->mysqlNumFields( $res->result );
 643                 for ( $i = 0; $i < $n; $i++ ) {
 644                         $meta = $this->mysqlFetchField( $res->result, $i );
 645                         if ( $field == $meta->name ) {
 646                                 return new MySQLField( $meta );
 647                         }
 648                 }
 649
 650                 return false;
 651         }
 652
 653         /**
 654          * Get column information from a result
 655          *
 656          * @param resource $res Raw result
 657          * @param int $n
 658          * @return stdClass
 659          */
 660         abstract protected function mysqlFetchField( $res, $n );
 661
 662         /**
 663          * Get information about an index into an object
 664          * Returns false if the index does not exist
 665          *
 666          * @param string $table
 667          * @param string $index
 668          * @param string $fname
 669          * @return bool|array|null False or null on failure
 670          */
 671         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 672                 # SHOW INDEX works in MySQL 3.23.58, but SHOW INDEXES does not.
 673                 # SHOW INDEX should work for 3.x and up:
 674                 # https://dev.mysql.com/doc/mysql/en/SHOW_INDEX.html
 675                 $table = $this->tableName( $table );
 676                 $index = $this->indexName( $index );
 677
 678                 $sql = 'SHOW INDEX FROM ' . $table;
 679                 $res = $this->query( $sql, $fname );
 680
 681                 if ( !$res ) {
 682                         return null;
 683                 }
 684
 685                 $result = [];
 686
 687                 foreach ( $res as $row ) {
 688                         if ( $row->Key_name == $index ) {
 689                                 $result[] = $row;
 690                         }
 691                 }
 692
 693                 return $result ?: false;
 694         }
 695
 696         /**
 697          * @param string $s
 698          * @return string
 699          */
 700         public function strencode( $s ) {
 701                 return $this->mysqlRealEscapeString( $s );
 702         }
 703
 704         /**
 705          * @param string $s
 706          * @return mixed
 707          */
 708         abstract protected function mysqlRealEscapeString( $s );
 709
 710         public function addQuotes( $s ) {
 711                 if ( is_bool( $s ) ) {
 712                         // Parent would transform to int, which does not play nice with MySQL type juggling.
 713                         // When searching for an int in a string column, the strings are cast to int, which
 714                         // means false would match any string not starting with a number.
 715                         $s = (string)(int)$s;
 716                 }
 717                 return parent::addQuotes( $s );
 718         }
 719
 720         /**
 721          * MySQL uses `backticks` for identifier quoting instead of the sql standard "double quotes".
 722          *
 723          * @param string $s
 724          * @return string
 725          */
 726         public function addIdentifierQuotes( $s ) {
 727                 // Characters in the range \u0001-\uFFFF are valid in a quoted identifier
 728                 // Remove NUL bytes and escape backticks by doubling
 729                 return '`' . str_replace( [ "\0", '`' ], [ '', '``' ], $s ) . '`';
 730         }
 731
 732         /**
 733          * @param string $name
 734          * @return bool
 735          */
 736         public function isQuotedIdentifier( $name ) {
 737                 return strlen( $name ) && $name[0] == '`' && substr( $name, -1, 1 ) == '`';
 738         }
 739
 740         public function getLag() {
 741                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 742                         return $this->getLagFromPtHeartbeat();
 743                 } else {
 744                         return $this->getLagFromSlaveStatus();
 745                 }
 746         }
 747
 748         /**
 749          * @return string
 750          */
 751         protected function getLagDetectionMethod() {
 752                 return $this->lagDetectionMethod;
 753         }
 754
 755         /**
 756          * @return bool|int
 757          */
 758         protected function getLagFromSlaveStatus() {
 759                 $res = $this->query( 'SHOW SLAVE STATUS', __METHOD__ );
 760                 $row = $res ? $res->fetchObject() : false;
 761                 // If the server is not replicating, there will be no row
 762                 if ( $row && strval( $row->Seconds_Behind_Master ) !== '' ) {
 763                         return intval( $row->Seconds_Behind_Master );
 764                 }
 765
 766                 return false;
 767         }
 768
 769         /**
 770          * @return bool|float
 771          */
 772         protected function getLagFromPtHeartbeat() {
 773                 $options = $this->lagDetectionOptions;
 774
 775                 $currentTrxInfo = $this->getRecordedTransactionLagStatus();
 776                 if ( $currentTrxInfo ) {
 777                         // There is an active transaction and the initial lag was already queried
 778                         $staleness = microtime( true ) - $currentTrxInfo['since'];
 779                         if ( $staleness > self::LAG_STALE_WARN_THRESHOLD ) {
 780                                 // Avoid returning higher and higher lag value due to snapshot age
 781                                 // given that the isolation level will typically be REPEATABLE-READ
 782                                 $this->queryLogger->warning(
 783                                         "Using cached lag value for {db_server} due to active transaction",
 784                                         $this->getLogContext( [ 'method' => __METHOD__, 'age' => $staleness ] )
 785                                 );
 786                         }
 787
 788                         return $currentTrxInfo['lag'];
 789                 }
 790
 791                 if ( isset( $options['conds'] ) ) {
 792                         // Best method for multi-DC setups: use logical channel names
 793                         $data = $this->getHeartbeatData( $options['conds'] );
 794                 } else {
 795                         // Standard method: use master server ID (works with stock pt-heartbeat)
 796                         $masterInfo = $this->getMasterServerInfo();
 797                         if ( !$masterInfo ) {
 798                                 $this->queryLogger->error(
 799                                         "Unable to query master of {db_server} for server ID",
 800                                         $this->getLogContext( [
 801                                                 'method' => __METHOD__
 802                                         ] )
 803                                 );
 804
 805                                 return false; // could not get master server ID
 806                         }
 807
 808                         $conds = [ 'server_id' => intval( $masterInfo['serverId'] ) ];
 809                         $data = $this->getHeartbeatData( $conds );
 810                 }
 811
 812                 list( $time, $nowUnix ) = $data;
 813                 if ( $time !== null ) {
 814                         // @time is in ISO format like "2015-09-25T16:48:10.000510"
 815                         $dateTime = new DateTime( $time, new DateTimeZone( 'UTC' ) );
 816                         $timeUnix = (int)$dateTime->format( 'U' ) + $dateTime->format( 'u' ) / 1e6;
 817
 818                         return max( $nowUnix - $timeUnix, 0.0 );
 819                 }
 820
 821                 $this->queryLogger->error(
 822                         "Unable to find pt-heartbeat row for {db_server}",
 823                         $this->getLogContext( [
 824                                 'method' => __METHOD__
 825                         ] )
 826                 );
 827
 828                 return false;
 829         }
 830
 831         protected function getMasterServerInfo() {
 832                 $cache = $this->srvCache;
 833                 $key = $cache->makeGlobalKey(
 834                         'mysql',
 835                         'master-info',
 836                         // Using one key for all cluster replica DBs is preferable
 837                         $this->getLBInfo( 'clusterMasterHost' ) ?: $this->getServer()
 838                 );
 839
 840                 return $cache->getWithSetCallback(
 841                         $key,
 842                         $cache::TTL_INDEFINITE,
 843                         function () use ( $cache, $key ) {
 844                                 // Get and leave a lock key in place for a short period
 845                                 if ( !$cache->lock( $key, 0, 10 ) ) {
 846                                         return false; // avoid master connection spike slams
 847                                 }
 848
 849                                 $conn = $this->getLazyMasterHandle();
 850                                 if ( !$conn ) {
 851                                         return false; // something is misconfigured
 852                                 }
 853
 854                                 // Connect to and query the master; catch errors to avoid outages
 855                                 try {
 856                                         $res = $conn->query( 'SELECT @@server_id AS id', __METHOD__ );
 857                                         $row = $res ? $res->fetchObject() : false;
 858                                         $id = $row ? (int)$row->id : 0;
 859                                 } catch ( DBError $e ) {
 860                                         $id = 0;
 861                                 }
 862
 863                                 // Cache the ID if it was retrieved
 864                                 return $id ? [ 'serverId' => $id, 'asOf' => time() ] : false;
 865                         }
 866                 );
 867         }
 868
 869         /**
 870          * @param array $conds WHERE clause conditions to find a row
 871          * @return array (heartbeat `ts` column value or null, UNIX timestamp) for the newest beat
 872          * @see https://www.percona.com/doc/percona-toolkit/2.1/pt-heartbeat.html
 873          */
 874         protected function getHeartbeatData( array $conds ) {
 875                 // Query time and trip time are not counted
 876                 $nowUnix = microtime( true );
 877                 // Do not bother starting implicit transactions here
 878                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
 879                 try {
 880                         $whereSQL = $this->makeList( $conds, self::LIST_AND );
 881                         // Use ORDER BY for channel based queries since that field might not be UNIQUE.
 882                         // Note: this would use "TIMESTAMPDIFF(MICROSECOND,ts,UTC_TIMESTAMP(6))" but the
 883                         // percision field is not supported in MySQL <= 5.5.
 884                         $res = $this->query(
 885                                 "SELECT ts FROM heartbeat.heartbeat WHERE $whereSQL ORDER BY ts DESC LIMIT 1",
 886                                 __METHOD__
 887                         );
 888                         $row = $res ? $res->fetchObject() : false;
 889                 } finally {
 890                         $this->restoreFlags();
 891                 }
 892
 893                 return [ $row ? $row->ts : null, $nowUnix ];
 894         }
 895
 896         protected function getApproximateLagStatus() {
 897                 if ( $this->getLagDetectionMethod() === 'pt-heartbeat' ) {
 898                         // Disable caching since this is fast enough and we don't wan't
 899                         // to be *too* pessimistic by having both the cache TTL and the
 900                         // pt-heartbeat interval count as lag in getSessionLagStatus()
 901                         return parent::getApproximateLagStatus();
 902                 }
 903
 904                 $key = $this->srvCache->makeGlobalKey( 'mysql-lag', $this->getServer() );
 905                 $approxLag = $this->srvCache->get( $key );
 906                 if ( !$approxLag ) {
 907                         $approxLag = parent::getApproximateLagStatus();
 908                         $this->srvCache->set( $key, $approxLag, 1 );
 909                 }
 910
 911                 return $approxLag;
 912         }
 913
 914         public function masterPosWait( DBMasterPos $pos, $timeout ) {
 915                 if ( !( $pos instanceof MySQLMasterPos ) ) {
 916                         throw new InvalidArgumentException( "Position not an instance of MySQLMasterPos" );
 917                 }
 918
 919                 if ( $this->getLBInfo( 'is static' ) === true ) {
 920                         return 0; // this is a copy of a read-only dataset with no master DB
 921                 } elseif ( $this->lastKnownReplicaPos && $this->lastKnownReplicaPos->hasReached( $pos ) ) {
 922                         return 0; // already reached this point for sure
 923                 }
 924
 925                 // Call doQuery() directly, to avoid opening a transaction if DBO_TRX is set
 926                 if ( $pos->getGTIDs() ) {
 927                         // Ignore GTIDs from domains exclusive to the master DB (presumably inactive)
 928                         $rpos = $this->getReplicaPos();
 929                         $gtidsWait = $rpos ? MySQLMasterPos::getCommonDomainGTIDs( $pos, $rpos ) : [];
 930                         if ( !$gtidsWait ) {
 931                                 $this->queryLogger->error(
 932                                         "No GTIDs with the same domain between master ($pos) and replica ($rpos)",
 933                                         $this->getLogContext( [
 934                                                 'method' => __METHOD__,
 935                                         ] )
 936                                 );
 937
 938                                 return -1; // $pos is from the wrong cluster?
 939                         }
 940                         // Wait on the GTID set (MariaDB only)
 941                         $gtidArg = $this->addQuotes( implode( ',', $gtidsWait ) );
 942                         if ( strpos( $gtidArg, ':' ) !== false ) {
 943                                 // MySQL GTIDs, e.g "source_id:transaction_id"
 944                                 $res = $this->doQuery( "SELECT WAIT_FOR_EXECUTED_GTID_SET($gtidArg, $timeout)" );
 945                         } else {
 946                                 // MariaDB GTIDs, e.g."domain:server:sequence"
 947                                 $res = $this->doQuery( "SELECT MASTER_GTID_WAIT($gtidArg, $timeout)" );
 948                         }
 949                 } else {
 950                         // Wait on the binlog coordinates
 951                         $encFile = $this->addQuotes( $pos->getLogFile() );
 952                         $encPos = intval( $pos->getLogPosition()[$pos::CORD_EVENT] );
 953                         $res = $this->doQuery( "SELECT MASTER_POS_WAIT($encFile, $encPos, $timeout)" );
 954                 }
 955
 956                 $row = $res ? $this->fetchRow( $res ) : false;
 957                 if ( !$row ) {
 958                         throw new DBExpectedError( $this, "Replication wait failed: {$this->lastError()}" );
 959                 }
 960
 961                 // Result can be NULL (error), -1 (timeout), or 0+ per the MySQL manual
 962                 $status = ( $row[0] !== null ) ? intval( $row[0] ) : null;
 963                 if ( $status === null ) {
 964                         if ( !$pos->getGTIDs() ) {
 965                                 // T126436: jobs programmed to wait on master positions might be referencing
 966                                 // binlogs with an old master hostname; this makes MASTER_POS_WAIT() return null.
 967                                 // Try to detect this case and treat the replica DB as having reached the given
 968                                 // position (any master switchover already requires that the new master be caught
 969                                 // up before the switch).
 970                                 $replicationPos = $this->getReplicaPos();
 971                                 if ( $replicationPos && !$replicationPos->channelsMatch( $pos ) ) {
 972                                         $this->lastKnownReplicaPos = $replicationPos;
 973                                         $status = 0;
 974                                 }
 975                         }
 976                 } elseif ( $status >= 0 ) {
 977                         // Remember that this position was reached to save queries next time
 978                         $this->lastKnownReplicaPos = $pos;
 979                 }
 980
 981                 return $status;
 982         }
 983
 984         /**
 985          * Get the position of the master from SHOW SLAVE STATUS
 986          *
 987          * @return MySQLMasterPos|bool
 988          */
 989         public function getReplicaPos() {
 990                 $now = microtime( true ); // as-of-time *before* fetching GTID variables
 991
 992                 if ( $this->useGTIDs() ) {
 993                         // Try to use GTIDs, fallbacking to binlog positions if not possible
 994                         $data = $this->getServerGTIDs( __METHOD__ );
 995                         // Use gtid_slave_pos for MariaDB and gtid_executed for MySQL
 996                         foreach ( [ 'gtid_slave_pos', 'gtid_executed' ] as $name ) {
 997                                 if ( isset( $data[$name] ) && strlen( $data[$name] ) ) {
 998                                         return new MySQLMasterPos( $data[$name], $now );
 999                                 }
1000                         }
1001                 }
1002
1003                 $data = $this->getServerRoleStatus( 'SLAVE', __METHOD__ );
1004                 if ( $data && strlen( $data['Relay_Master_Log_File'] ) ) {
1005                         return new MySQLMasterPos(
1006                                 "{$data['Relay_Master_Log_File']}/{$data['Exec_Master_Log_Pos']}",
1007                                 $now
1008                         );
1009                 }
1010
1011                 return false;
1012         }
1013
1014         /**
1015          * Get the position of the master from SHOW MASTER STATUS
1016          *
1017          * @return MySQLMasterPos|bool
1018          */
1019         public function getMasterPos() {
1020                 $now = microtime( true ); // as-of-time *before* fetching GTID variables
1021
1022                 $pos = false;
1023                 if ( $this->useGTIDs() ) {
1024                         // Try to use GTIDs, fallbacking to binlog positions if not possible
1025                         $data = $this->getServerGTIDs( __METHOD__ );
1026                         // Use gtid_binlog_pos for MariaDB and gtid_executed for MySQL
1027                         foreach ( [ 'gtid_binlog_pos', 'gtid_executed' ] as $name ) {
1028                                 if ( isset( $data[$name] ) && strlen( $data[$name] ) ) {
1029                                         $pos = new MySQLMasterPos( $data[$name], $now );
1030                                         break;
1031                                 }
1032                         }
1033                         // Filter domains that are inactive or not relevant to the session
1034                         if ( $pos ) {
1035                                 $pos->setActiveOriginServerId( $this->getServerId() );
1036                                 $pos->setActiveOriginServerUUID( $this->getServerUUID() );
1037                                 if ( isset( $data['gtid_domain_id'] ) ) {
1038                                         $pos->setActiveDomain( $data['gtid_domain_id'] );
1039                                 }
1040                         }
1041                 }
1042
1043                 if ( !$pos ) {
1044                         $data = $this->getServerRoleStatus( 'MASTER', __METHOD__ );
1045                         if ( $data && strlen( $data['File'] ) ) {
1046                                 $pos = new MySQLMasterPos( "{$data['File']}/{$data['Position']}", $now );
1047                         }
1048                 }
1049
1050                 return $pos;
1051         }
1052
1053         /**
1054          * @return int
1055          * @throws DBQueryError If the variable doesn't exist for some reason
1056          */
1057         protected function getServerId() {
1058                 return $this->srvCache->getWithSetCallback(
1059                         $this->srvCache->makeGlobalKey( 'mysql-server-id', $this->getServer() ),
1060                         self::SERVER_ID_CACHE_TTL,
1061                         function () {
1062                                 $res = $this->query( "SELECT @@server_id AS id", __METHOD__ );
1063                                 return intval( $this->fetchObject( $res )->id );
1064                         }
1065                 );
1066         }
1067
1068         /**
1069          * @return string|null
1070          */
1071         protected function getServerUUID() {
1072                 return $this->srvCache->getWithSetCallback(
1073                         $this->srvCache->makeGlobalKey( 'mysql-server-uuid', $this->getServer() ),
1074                         self::SERVER_ID_CACHE_TTL,
1075                         function () {
1076                                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'server_uuid'" );
1077                                 $row = $this->fetchObject( $res );
1078
1079                                 return $row ? $row->Value : null;
1080                         }
1081                 );
1082         }
1083
1084         /**
1085          * @param string $fname
1086          * @return string[]
1087          */
1088         protected function getServerGTIDs( $fname = __METHOD__ ) {
1089                 $map = [];
1090                 // Get global-only variables like gtid_executed
1091                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'gtid_%'", $fname );
1092                 foreach ( $res as $row ) {
1093                         $map[$row->Variable_name] = $row->Value;
1094                 }
1095                 // Get session-specific (e.g. gtid_domain_id since that is were writes will log)
1096                 $res = $this->query( "SHOW SESSION VARIABLES LIKE 'gtid_%'", $fname );
1097                 foreach ( $res as $row ) {
1098                         $map[$row->Variable_name] = $row->Value;
1099                 }
1100
1101                 return $map;
1102         }
1103
1104         /**
1105          * @param string $role One of "MASTER"/"SLAVE"
1106          * @param string $fname
1107          * @return string[] Latest available server status row
1108          */
1109         protected function getServerRoleStatus( $role, $fname = __METHOD__ ) {
1110                 return $this->query( "SHOW $role STATUS", $fname )->fetchRow() ?: [];
1111         }
1112
1113         public function serverIsReadOnly() {
1114                 $res = $this->query( "SHOW GLOBAL VARIABLES LIKE 'read_only'", __METHOD__ );
1115                 $row = $this->fetchObject( $res );
1116
1117                 return $row ? ( strtolower( $row->Value ) === 'on' ) : false;
1118         }
1119
1120         /**
1121          * @param string $index
1122          * @return string
1123          */
1124         function useIndexClause( $index ) {
1125                 return "FORCE INDEX (" . $this->indexName( $index ) . ")";
1126         }
1127
1128         /**
1129          * @param string $index
1130          * @return string
1131          */
1132         function ignoreIndexClause( $index ) {
1133                 return "IGNORE INDEX (" . $this->indexName( $index ) . ")";
1134         }
1135
1136         /**
1137          * @return string
1138          */
1139         function lowPriorityOption() {
1140                 return 'LOW_PRIORITY';
1141         }
1142
1143         /**
1144          * @return string
1145          */
1146         public function getSoftwareLink() {
1147                 // MariaDB includes its name in its version string; this is how MariaDB's version of
1148                 // the mysql command-line client identifies MariaDB servers (see mariadb_connection()
1149                 // in libmysql/libmysql.c).
1150                 $version = $this->getServerVersion();
1151                 if ( strpos( $version, 'MariaDB' ) !== false || strpos( $version, '-maria-' ) !== false ) {
1152                         return '[{{int:version-db-mariadb-url}} MariaDB]';
1153                 }
1154
1155                 // Percona Server's version suffix is not very distinctive, and @@version_comment
1156                 // doesn't give the necessary info for source builds, so assume the server is MySQL.
1157                 // (Even Percona's version of mysql doesn't try to make the distinction.)
1158                 return '[{{int:version-db-mysql-url}} MySQL]';
1159         }
1160
1161         /**
1162          * @return string
1163          */
1164         public function getServerVersion() {
1165                 // Not using mysql_get_server_info() or similar for consistency: in the handshake,
1166                 // MariaDB 10 adds the prefix "5.5.5-", and only some newer client libraries strip
1167                 // it off (see RPL_VERSION_HACK in include/mysql_com.h).
1168                 if ( $this->serverVersion === null ) {
1169                         $this->serverVersion = $this->selectField( '', 'VERSION()', '', __METHOD__ );
1170                 }
1171                 return $this->serverVersion;
1172         }
1173
1174         /**
1175          * @param array $options
1176          */
1177         public function setSessionOptions( array $options ) {
1178                 if ( isset( $options['connTimeout'] ) ) {
1179                         $timeout = (int)$options['connTimeout'];
1180                         $this->query( "SET net_read_timeout=$timeout" );
1181                         $this->query( "SET net_write_timeout=$timeout" );
1182                 }
1183         }
1184
1185         /**
1186          * @param string &$sql
1187          * @param string &$newLine
1188          * @return bool
1189          */
1190         public function streamStatementEnd( &$sql, &$newLine ) {
1191                 if ( strtoupper( substr( $newLine, 0, 9 ) ) == 'DELIMITER' ) {
1192                         preg_match( '/^DELIMITER\s+(\S+)/', $newLine, $m );
1193                         $this->delimiter = $m[1];
1194                         $newLine = '';
1195                 }
1196
1197                 return parent::streamStatementEnd( $sql, $newLine );
1198         }
1199
1200         /**
1201          * Check to see if a named lock is available. This is non-blocking.
1202          *
1203          * @param string $lockName Name of lock to poll
1204          * @param string $method Name of method calling us
1205          * @return bool
1206          * @since 1.20
1207          */
1208         public function lockIsFree( $lockName, $method ) {
1209                 if ( !parent::lockIsFree( $lockName, $method ) ) {
1210                         return false; // already held
1211                 }
1212
1213                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1214                 $result = $this->query( "SELECT IS_FREE_LOCK($encName) AS lockstatus", $method );
1215                 $row = $this->fetchObject( $result );
1216
1217                 return ( $row->lockstatus == 1 );
1218         }
1219
1220         /**
1221          * @param string $lockName
1222          * @param string $method
1223          * @param int $timeout
1224          * @return bool
1225          */
1226         public function lock( $lockName, $method, $timeout = 5 ) {
1227                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1228                 $result = $this->query( "SELECT GET_LOCK($encName, $timeout) AS lockstatus", $method );
1229                 $row = $this->fetchObject( $result );
1230
1231                 if ( $row->lockstatus == 1 ) {
1232                         parent::lock( $lockName, $method, $timeout ); // record
1233                         return true;
1234                 }
1235
1236                 $this->queryLogger->info( __METHOD__ . " failed to acquire lock '{lockname}'",
1237                         [ 'lockname' => $lockName ] );
1238
1239                 return false;
1240         }
1241
1242         /**
1243          * FROM MYSQL DOCS:
1244          * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
1245          * @param string $lockName
1246          * @param string $method
1247          * @return bool
1248          */
1249         public function unlock( $lockName, $method ) {
1250                 $encName = $this->addQuotes( $this->makeLockName( $lockName ) );
1251                 $result = $this->query( "SELECT RELEASE_LOCK($encName) as lockstatus", $method );
1252                 $row = $this->fetchObject( $result );
1253
1254                 if ( $row->lockstatus == 1 ) {
1255                         parent::unlock( $lockName, $method ); // record
1256                         return true;
1257                 }
1258
1259                 $this->queryLogger->warning( __METHOD__ . " failed to release lock '$lockName'\n" );
1260
1261                 return false;
1262         }
1263
1264         private function makeLockName( $lockName ) {
1265                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1266                 // Newer version enforce a 64 char length limit.
1267                 return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
1268         }
1269
1270         public function namedLocksEnqueue() {
1271                 return true;
1272         }
1273
1274         public function tableLocksHaveTransactionScope() {
1275                 return false; // tied to TCP connection
1276         }
1277
1278         protected function doLockTables( array $read, array $write, $method ) {
1279                 $items = [];
1280                 foreach ( $write as $table ) {
1281                         $items[] = $this->tableName( $table ) . ' WRITE';
1282                 }
1283                 foreach ( $read as $table ) {
1284                         $items[] = $this->tableName( $table ) . ' READ';
1285                 }
1286
1287                 $sql = "LOCK TABLES " . implode( ',', $items );
1288                 $this->query( $sql, $method );
1289
1290                 return true;
1291         }
1292
1293         protected function doUnlockTables( $method ) {
1294                 $this->query( "UNLOCK TABLES", $method );
1295
1296                 return true;
1297         }
1298
1299         /**
1300          * @param bool $value
1301          */
1302         public function setBigSelects( $value = true ) {
1303                 if ( $value === 'default' ) {
1304                         if ( $this->defaultBigSelects === null ) {
1305                                 # Function hasn't been called before so it must already be set to the default
1306                                 return;
1307                         } else {
1308                                 $value = $this->defaultBigSelects;
1309                         }
1310                 } elseif ( $this->defaultBigSelects === null ) {
1311                         $this->defaultBigSelects =
1312                                 (bool)$this->selectField( false, '@@sql_big_selects', '', __METHOD__ );
1313                 }
1314                 $encValue = $value ? '1' : '0';
1315                 $this->query( "SET sql_big_selects=$encValue", __METHOD__ );
1316         }
1317
1318         /**
1319          * DELETE where the condition is a join. MySql uses multi-table deletes.
1320          * @param string $delTable
1321          * @param string $joinTable
1322          * @param string $delVar
1323          * @param string $joinVar
1324          * @param array|string $conds
1325          * @param bool|string $fname
1326          * @throws DBUnexpectedError
1327          * @return bool|ResultWrapper
1328          */
1329         public function deleteJoin(
1330                 $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = __METHOD__
1331         ) {
1332                 if ( !$conds ) {
1333                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
1334                 }
1335
1336                 $delTable = $this->tableName( $delTable );
1337                 $joinTable = $this->tableName( $joinTable );
1338                 $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
1339
1340                 if ( $conds != '*' ) {
1341                         $sql .= ' AND ' . $this->makeList( $conds, self::LIST_AND );
1342                 }
1343
1344                 return $this->query( $sql, $fname );
1345         }
1346
1347         /**
1348          * @param string $table
1349          * @param array $rows
1350          * @param array $uniqueIndexes
1351          * @param array $set
1352          * @param string $fname
1353          * @return bool
1354          */
1355         public function upsert( $table, array $rows, array $uniqueIndexes,
1356                 array $set, $fname = __METHOD__
1357         ) {
1358                 if ( !count( $rows ) ) {
1359                         return true; // nothing to do
1360                 }
1361
1362                 if ( !is_array( reset( $rows ) ) ) {
1363                         $rows = [ $rows ];
1364                 }
1365
1366                 $table = $this->tableName( $table );
1367                 $columns = array_keys( $rows[0] );
1368
1369                 $sql = "INSERT INTO $table (" . implode( ',', $columns ) . ') VALUES ';
1370                 $rowTuples = [];
1371                 foreach ( $rows as $row ) {
1372                         $rowTuples[] = '(' . $this->makeList( $row ) . ')';
1373                 }
1374                 $sql .= implode( ',', $rowTuples );
1375                 $sql .= " ON DUPLICATE KEY UPDATE " . $this->makeList( $set, self::LIST_SET );
1376
1377                 return (bool)$this->query( $sql, $fname );
1378         }
1379
1380         /**
1381          * Determines how long the server has been up
1382          *
1383          * @return int
1384          */
1385         public function getServerUptime() {
1386                 $vars = $this->getMysqlStatus( 'Uptime' );
1387
1388                 return (int)$vars['Uptime'];
1389         }
1390
1391         /**
1392          * Determines if the last failure was due to a deadlock
1393          *
1394          * @return bool
1395          */
1396         public function wasDeadlock() {
1397                 return $this->lastErrno() == 1213;
1398         }
1399
1400         /**
1401          * Determines if the last failure was due to a lock timeout
1402          *
1403          * @return bool
1404          */
1405         public function wasLockTimeout() {
1406                 return $this->lastErrno() == 1205;
1407         }
1408
1409         /**
1410          * Determines if the last failure was due to the database being read-only.
1411          *
1412          * @return bool
1413          */
1414         public function wasReadOnlyError() {
1415                 return $this->lastErrno() == 1223 ||
1416                         ( $this->lastErrno() == 1290 && strpos( $this->lastError(), '--read-only' ) !== false );
1417         }
1418
1419         public function wasConnectionError( $errno ) {
1420                 return $errno == 2013 || $errno == 2006;
1421         }
1422
1423         protected function wasKnownStatementRollbackError() {
1424                 $errno = $this->lastErrno();
1425
1426                 if ( $errno === 1205 ) { // lock wait timeout
1427                         // Note that this is uncached to avoid stale values of SET is used
1428                         $row = $this->selectRow(
1429                                 false,
1430                                 [ 'innodb_rollback_on_timeout' => '@@innodb_rollback_on_timeout' ],
1431                                 [],
1432                                 __METHOD__
1433                         );
1434                         // https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
1435                         // https://dev.mysql.com/doc/refman/5.5/en/innodb-parameters.html
1436                         return $row->innodb_rollback_on_timeout ? false : true;
1437                 }
1438
1439                 // See https://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html
1440                 return in_array( $errno, [ 1022, 1216, 1217, 1137 ], true );
1441         }
1442
1443         /**
1444          * @param string $oldName
1445          * @param string $newName
1446          * @param bool $temporary
1447          * @param string $fname
1448          * @return bool
1449          */
1450         public function duplicateTableStructure(
1451                 $oldName, $newName, $temporary = false, $fname = __METHOD__
1452         ) {
1453                 $tmp = $temporary ? 'TEMPORARY ' : '';
1454                 $newName = $this->addIdentifierQuotes( $newName );
1455                 $oldName = $this->addIdentifierQuotes( $oldName );
1456                 $query = "CREATE $tmp TABLE $newName (LIKE $oldName)";
1457
1458                 return $this->query( $query, $fname );
1459         }
1460
1461         /**
1462          * List all tables on the database
1463          *
1464          * @param string $prefix Only show tables with this prefix, e.g. mw_
1465          * @param string $fname Calling function name
1466          * @return array
1467          */
1468         public function listTables( $prefix = null, $fname = __METHOD__ ) {
1469                 $result = $this->query( "SHOW TABLES", $fname );
1470
1471                 $endArray = [];
1472
1473                 foreach ( $result as $table ) {
1474                         $vars = get_object_vars( $table );
1475                         $table = array_pop( $vars );
1476
1477                         if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
1478                                 $endArray[] = $table;
1479                         }
1480                 }
1481
1482                 return $endArray;
1483         }
1484
1485         /**
1486          * @param string $tableName
1487          * @param string $fName
1488          * @return bool|ResultWrapper
1489          */
1490         public function dropTable( $tableName, $fName = __METHOD__ ) {
1491                 if ( !$this->tableExists( $tableName, $fName ) ) {
1492                         return false;
1493                 }
1494
1495                 return $this->query( "DROP TABLE IF EXISTS " . $this->tableName( $tableName ), $fName );
1496         }
1497
1498         /**
1499          * Get status information from SHOW STATUS in an associative array
1500          *
1501          * @param string $which
1502          * @return array
1503          */
1504         private function getMysqlStatus( $which = "%" ) {
1505                 $res = $this->query( "SHOW STATUS LIKE '{$which}'" );
1506                 $status = [];
1507
1508                 foreach ( $res as $row ) {
1509                         $status[$row->Variable_name] = $row->Value;
1510                 }
1511
1512                 return $status;
1513         }
1514
1515         /**
1516          * Lists VIEWs in the database
1517          *
1518          * @param string $prefix Only show VIEWs with this prefix, eg.
1519          * unit_test_, or $wgDBprefix. Default: null, would return all views.
1520          * @param string $fname Name of calling function
1521          * @return array
1522          * @since 1.22
1523          */
1524         public function listViews( $prefix = null, $fname = __METHOD__ ) {
1525                 // The name of the column containing the name of the VIEW
1526                 $propertyName = 'Tables_in_' . $this->dbName;
1527
1528                 // Query for the VIEWS
1529                 $res = $this->query( 'SHOW FULL TABLES WHERE TABLE_TYPE = "VIEW"' );
1530                 $allViews = [];
1531                 foreach ( $res as $row ) {
1532                         array_push( $allViews, $row->$propertyName );
1533                 }
1534
1535                 if ( is_null( $prefix ) || $prefix === '' ) {
1536                         return $allViews;
1537                 }
1538
1539                 $filteredViews = [];
1540                 foreach ( $allViews as $viewName ) {
1541                         // Does the name of this VIEW start with the table-prefix?
1542                         if ( strpos( $viewName, $prefix ) === 0 ) {
1543                                 array_push( $filteredViews, $viewName );
1544                         }
1545                 }
1546
1547                 return $filteredViews;
1548         }
1549
1550         /**
1551          * Differentiates between a TABLE and a VIEW.
1552          *
1553          * @param string $name Name of the TABLE/VIEW to test
1554          * @param string $prefix
1555          * @return bool
1556          * @since 1.22
1557          */
1558         public function isView( $name, $prefix = null ) {
1559                 return in_array( $name, $this->listViews( $prefix ) );
1560         }
1561
1562         protected function isTransactableQuery( $sql ) {
1563                 return parent::isTransactableQuery( $sql ) &&
1564                         !preg_match( '/^SELECT\s+(GET|RELEASE|IS_FREE)_LOCK\(/', $sql );
1565         }
1566
1567         /**
1568          * @param string $field Field or column to cast
1569          * @return string
1570          */
1571         public function buildIntegerCast( $field ) {
1572                 return 'CAST( ' . $field . ' AS SIGNED )';
1573         }
1574
1575         /*
1576          * @return bool Whether GTID support is used (mockable for testing)
1577          */
1578         protected function useGTIDs() {
1579                 return $this->useGTIDs;
1580         }
1581 }
1582
1583 class_alias( DatabaseMysqlBase::class, 'DatabaseMysqlBase' );