DatabaseMySQL.php

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<?php
namespace Wikimedia\Rdbms;
 
use mysqli;
use mysqli_result;
use RuntimeException;
use Wikimedia\AtEase\AtEase;
use Wikimedia\IPUtils;
use Wikimedia\Rdbms\Platform\MySQLPlatform;
use Wikimedia\Rdbms\Platform\SQLPlatform;
use Wikimedia\Rdbms\Replication\MysqlReplicationReporter;
 
class DatabaseMySQL extends Database {
    private $sslKeyPath;
    private $sslCertPath;
    private $sslCAFile;
    private $sslCAPath;
    private $sslCiphers;
    private $utf8Mode;
 
    protected $platform;
 
    protected $replicationReporter;
    private $sessionLastAutoRowId;
 
    public function __construct( array $params ) {
        foreach ( [ 'KeyPath', 'CertPath', 'CAFile', 'CAPath', 'Ciphers' ] as $name ) {
            $var = "ssl{$name}";
            if ( isset( $params[$var] ) ) {
                $this->$var = $params[$var];
            }
        }
        $this->utf8Mode = !empty( $params['utf8Mode'] );
        parent::__construct( $params );
        $this->platform = new MySQLPlatform(
            $this,
            $this->logger,
            $this->currentDomain,
            $this->errorLogger
        );
        $this->replicationReporter = new MysqlReplicationReporter(
            $params['topologyRole'],
            $this->logger,
            $params['srvCache'],
            $params['lagDetectionMethod'] ?? 'Seconds_Behind_Master',
            $params['lagDetectionOptions'] ?? [],
            !empty( $params['useGTIDs' ] )
        );
    }
 
    public function getType() {
        return 'mysql';
    }
 
    protected function open( $server, $user, $password, $db, $schema, $tablePrefix ) {
        $this->close( __METHOD__ );
 
        if ( $schema !== null ) {
            throw $this->newExceptionAfterConnectError( "Got schema '$schema'; not supported." );
        }
 
        $this->installErrorHandler();
        try {
            $this->conn = $this->mysqlConnect( $server, $user, $password, $db );
        } catch ( RuntimeException $e ) {
            $this->restoreErrorHandler();
            throw $this->newExceptionAfterConnectError( $e->getMessage() );
        }
        $error = $this->restoreErrorHandler();
 
        if ( !$this->conn ) {
            throw $this->newExceptionAfterConnectError( $error ?: $this->lastError() );
        }
 
        try {
            $this->currentDomain = new DatabaseDomain(
                $db && strlen( $db ) ? $db : null,
                null,
                $tablePrefix
            );
            $this->platform->setPrefix( $tablePrefix );
 
            $set = [];
            if ( !$this->flagsHolder->getFlag( self::DBO_GAUGE ) ) {
                // Abstract over any excessive MySQL defaults
                $set[] = 'group_concat_max_len = 262144';
                // Set any custom settings defined by site config
                // https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html
                foreach ( $this->connectionVariables as $var => $val ) {
                    // Escape strings but not numbers to avoid MySQL complaining
                    if ( !is_int( $val ) && !is_float( $val ) ) {
                        $val = $this->addQuotes( $val );
                    }
                    $set[] = $this->platform->addIdentifierQuotes( $var ) . ' = ' . $val;
                }
            }
 
            if ( $set ) {
                $sql = 'SET ' . implode( ', ', $set );
                $flags = self::QUERY_NO_RETRY | self::QUERY_CHANGE_TRX;
                $query = new Query( $sql, $flags, 'SET' );
                // Avoid using query() so that replaceLostConnection() does not throw
                // errors if the transaction status is STATUS_TRX_ERROR
                $qs = $this->executeQuery( $query, __METHOD__, $flags );
                if ( $qs->res === false ) {
                    $this->reportQueryError( $qs->message, $qs->code, $sql, __METHOD__ );
                }
            }
        } catch ( RuntimeException $e ) {
            throw $this->newExceptionAfterConnectError( $e->getMessage() );
        }
    }
 
    protected function doSelectDomain( DatabaseDomain $domain ) {
        if ( $domain->getSchema() !== null ) {
            throw new DBExpectedError(
                $this,
                __CLASS__ . ": domain '{$domain->getId()}' has a schema component"
            );
        }
 
        $database = $domain->getDatabase();
        // A null database means "don't care" so leave it as is and update the table prefix
        if ( $database === null ) {
            $this->currentDomain = new DatabaseDomain(
                $this->currentDomain->getDatabase(),
                null,
                $domain->getTablePrefix()
            );
            $this->platform->setPrefix( $domain->getTablePrefix() );
 
            return true;
        }
 
        if ( $database !== $this->getDBname() ) {
            $sql = 'USE ' . $this->addIdentifierQuotes( $database );
            $query = new Query( $sql, self::QUERY_CHANGE_TRX, 'USE' );
            $qs = $this->executeQuery( $query, __METHOD__, self::QUERY_CHANGE_TRX );
            if ( $qs->res === false ) {
                $this->reportQueryError( $qs->message, $qs->code, $sql, __METHOD__ );
                return false; // unreachable
            }
        }
 
        // Update that domain fields on success (no exception thrown)
        $this->currentDomain = $domain;
        $this->platform->setPrefix( $domain->getTablePrefix() );
 
        return true;
    }
 
    public function lastError() {
        if ( $this->conn ) {
            // Even if it's non-zero, it can still be invalid
            $error = $this->mysqlError( $this->conn );
            if ( !$error ) {
                $error = $this->mysqlError();
            }
        } else {
            $error = $this->mysqlError() ?: $this->lastConnectError;
        }
 
        return $error;
    }
 
    protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
        $row = $this->replicationReporter->getReplicationSafetyInfo( $this );
        // For row-based-replication, the resulting changes will be relayed, not the query
        if ( $row->binlog_format === 'ROW' ) {
            return true;
        }
        // LIMIT requires ORDER BY on a unique key or it is non-deterministic
        if ( isset( $selectOptions['LIMIT'] ) ) {
            return false;
        }
        // In MySQL, an INSERT SELECT is only replication safe with row-based
        // replication or if innodb_autoinc_lock_mode is 0. When those
        // conditions aren't met, use non-native mode.
        // While we could try to determine if the insert is safe anyway by
        // checking if the target table has an auto-increment column that
        // isn't set in $varMap, that seems unlikely to be worth the extra
        // complexity.
        return (
            in_array( 'NO_AUTO_COLUMNS', $insertOptions ) ||
            (int)$row->innodb_autoinc_lock_mode === 0
        );
    }
 
    protected function checkInsertWarnings( Query $query, $fname ) {
        if ( $this->conn && $this->conn->warning_count ) {
            // Yeah it's weird. It's not iterable.
            $warnings = $this->conn->get_warnings();
            $done = $warnings === false;
            while ( !$done ) {
                if ( in_array( $warnings->errno, [
                    // List based on https://dev.mysql.com/doc/refman/8.0/en/sql-mode.html#ignore-effect-on-execution
                    1048, /* ER_BAD_NULL_ERROR */
                    1526, /* ER_NO_PARTITION_FOR_GIVEN_VALUE */
                    1748, /* ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SET */
                    1242, /* ER_SUBQUERY_NO_1_ROW */
                    1369, /* ER_VIEW_CHECK_FAILED */
                    // Truncation and overflow per T108255
                    1264, /* ER_WARN_DATA_OUT_OF_RANGE */
                    1265, /* WARN_DATA_TRUNCATED */
                ] ) ) {
                    $this->reportQueryError(
                        'Insert returned unacceptable warning: ' . $warnings->message,
                        $warnings->errno,
                        $query->getSQL(),
                        $fname
                    );
                }
                $done = !$warnings->next();
            }
        }
    }
 
    public function estimateRowCount(
        $tables,
        $var = '*',
        $conds = '',
        $fname = __METHOD__,
        $options = [],
        $join_conds = []
    ): int {
        $conds = $this->platform->normalizeConditions( $conds, $fname );
        $column = $this->platform->extractSingleFieldFromList( $var );
        if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
            $conds[] = "$column IS NOT NULL";
        }
 
        $options['EXPLAIN'] = true;
        $res = $this->select( $tables, $var, $conds, $fname, $options, $join_conds );
        if ( $res === false ) {
            return -1;
        }
        if ( !$res->numRows() ) {
            return 0;
        }
 
        $rows = 1;
        foreach ( $res as $plan ) {
            $rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
        }
 
        return (int)$rows;
    }
 
    public function tableExists( $table, $fname = __METHOD__ ) {
        $components = $this->platform->qualifiedTableComponents( $table );
        if ( count( $components ) === 1 ) {
            $db = $this->currentDomain->getDatabase();
            $tableName = $components[0];
        } elseif ( count( $components ) === 2 ) {
            [ $db, $tableName ] = $components;
        } else {
            throw new DBLanguageError( 'Too many table components' );
        }
 
        if ( isset( $this->sessionTempTables[$tableName] ) ) {
            return true; // already known to exist and won't be found in the query anyway
        }
        return (bool)$this->newSelectQueryBuilder()
            ->select( '1' )
            ->from( 'information_schema.tables' )
            ->where( [
                'table_schema' => $db,
                'table_name' => $tableName,
            ] )
            ->caller( $fname )
            ->fetchField();
    }
 
    public function fieldInfo( $table, $field ) {
        $query = new Query(
            "SELECT * FROM " . $this->tableName( $table ) . " LIMIT 1",
            self::QUERY_SILENCE_ERRORS | self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'SELECT'
        );
        $res = $this->query( $query, __METHOD__ );
        if ( !$res ) {
            return false;
        }
        '@phan-var MysqliResultWrapper $res';
        return $res->getInternalFieldInfo( $field );
    }
 
    public function indexInfo( $table, $index, $fname = __METHOD__ ) {
        # https://dev.mysql.com/doc/mysql/en/SHOW_INDEX.html
        $index = $this->platform->indexName( $index );
        $query = new Query(
            'SHOW INDEX FROM ' . $this->tableName( $table ),
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'SHOW'
        );
        $res = $this->query( $query, $fname );
 
        if ( !$res ) {
            return null;
        }
 
        $result = [];
 
        foreach ( $res as $row ) {
            if ( $row->Key_name == $index ) {
                $result[] = $row;
            }
        }
 
        return $result ?: false;
    }
 
    public function strencode( $s ) {
        return $this->mysqlRealEscapeString( $s );
    }
 
    public function serverIsReadOnly() {
        // Avoid SHOW to avoid internal temporary tables
        $flags = self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE;
        $query = new Query( "SELECT @@GLOBAL.read_only AS Value", $flags, 'SELECT' );
        $res = $this->query( $query, __METHOD__ );
        $row = $res->fetchObject();
 
        return $row && (bool)$row->Value;
    }
 
    public function getSoftwareLink() {
        [ $variant ] = $this->getMySqlServerVariant();
        if ( $variant === 'MariaDB' ) {
            return '[{{int:version-db-mariadb-url}} MariaDB]';
        }
 
        return '[{{int:version-db-mysql-url}} MySQL]';
    }
 
    private function getMySqlServerVariant() {
        $version = $this->getServerVersion();
 
        // MariaDB includes its name in its version string; this is how MariaDB's version of
        // the mysql command-line client identifies MariaDB servers.
        // https://dev.mysql.com/doc/refman/8.0/en/information-functions.html#function_version
        // https://mariadb.com/kb/en/version/
        $parts = explode( '-', $version, 2 );
        $number = $parts[0];
        $suffix = $parts[1] ?? '';
        if ( strpos( $suffix, 'MariaDB' ) !== false || strpos( $suffix, '-maria-' ) !== false ) {
            $vendor = 'MariaDB';
        } else {
            $vendor = 'MySQL';
        }
 
        return [ $vendor, $number ];
    }
 
    public function getServerVersion() {
        // MariaDB 10 adds the prefix "5.5.5-", and only some newer client libraries strip
        // it off (see RPL_VERSION_HACK in include/mysql_com.h).
        $version = $this->conn->server_info;
        if (
            str_starts_with( $version, '5.5.5-' ) &&
            ( str_contains( $version, 'MariaDB' ) || str_contains( $version, '-maria-' ) )
        ) {
            $version = substr( $version, strlen( '5.5.5-' ) );
        }
        return $version;
    }
 
    public function setSessionOptions( array $options ) {
        $sqlAssignments = [];
 
        if ( isset( $options['connTimeout'] ) ) {
            $encTimeout = (int)$options['connTimeout'];
            $sqlAssignments[] = "net_read_timeout=$encTimeout";
            $sqlAssignments[] = "net_write_timeout=$encTimeout";
        }
        if ( isset( $options['groupConcatMaxLen'] ) ) {
            $maxLength = (int)$options['groupConcatMaxLen'];
            $sqlAssignments[] = "group_concat_max_len=$maxLength";
        }
 
        if ( $sqlAssignments ) {
            $query = new Query(
                'SET ' . implode( ', ', $sqlAssignments ),
                self::QUERY_CHANGE_TRX | self::QUERY_CHANGE_NONE,
                'SET'
            );
            $this->query( $query, __METHOD__ );
        }
    }
 
    public function streamStatementEnd( &$sql, &$newLine ) {
        if ( preg_match( '/^DELIMITER\s+(\S+)/i', $newLine, $m ) ) {
            $this->delimiter = $m[1];
            $newLine = '';
        }
 
        return parent::streamStatementEnd( $sql, $newLine );
    }
 
    public function doLockIsFree( string $lockName, string $method ) {
        $query = new Query( $this->platform->lockIsFreeSQLText( $lockName ), self::QUERY_CHANGE_LOCKS, 'SELECT' );
        $res = $this->query( $query, $method );
        $row = $res->fetchObject();
 
        return ( $row->unlocked == 1 );
    }
 
    public function doLock( string $lockName, string $method, int $timeout ) {
        $query = new Query( $this->platform->lockSQLText( $lockName, $timeout ), self::QUERY_CHANGE_LOCKS, 'SELECT' );
        $res = $this->query( $query, $method );
        $row = $res->fetchObject();
 
        return ( $row->acquired !== null ) ? (float)$row->acquired : null;
    }
 
    public function doUnlock( string $lockName, string $method ) {
        $query = new Query( $this->platform->unlockSQLText( $lockName ), self::QUERY_CHANGE_LOCKS, 'SELECT' );
        $res = $this->query( $query, $method );
        $row = $res->fetchObject();
 
        return ( $row->released == 1 );
    }
 
    public function namedLocksEnqueue() {
        return true;
    }
 
    protected function doFlushSession( $fname ) {
        // Note that RELEASE_ALL_LOCKS() is not supported well enough to use here.
        // https://mariadb.com/kb/en/release_all_locks/
        $releaseLockFields = [];
        foreach ( $this->sessionNamedLocks as $name => $info ) {
            $encName = $this->addQuotes( $this->platform->makeLockName( $name ) );
            $releaseLockFields[] = "RELEASE_LOCK($encName)";
        }
        if ( $releaseLockFields ) {
            $sql = 'SELECT ' . implode( ',', $releaseLockFields );
            $flags = self::QUERY_CHANGE_LOCKS | self::QUERY_NO_RETRY;
            $query = new Query( $sql, $flags, 'SELECT' );
            $qs = $this->executeQuery( $query, __METHOD__, $flags );
            if ( $qs->res === false ) {
                $this->reportQueryError( $qs->message, $qs->code, $sql, $fname, true );
            }
        }
    }
 
    public function upsert( $table, array $rows, $uniqueKeys, array $set, $fname = __METHOD__ ) {
        $identityKey = $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return;
        }
        $this->platform->assertValidUpsertSetArray( $set, $identityKey, $rows );
 
        $encTable = $this->tableName( $table );
        [ $sqlColumns, $sqlTuples ] = $this->platform->makeInsertLists( $rows );
        $sqlColumnAssignments = $this->makeList( $set, self::LIST_SET );
        // No need to expose __NEW.* since buildExcludedValue() uses VALUES(column)
 
        // https://mariadb.com/kb/en/insert-on-duplicate-key-update/
        // https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html
        $sql =
            "INSERT INTO $encTable " .
            "($sqlColumns) VALUES $sqlTuples " .
            "ON DUPLICATE KEY UPDATE $sqlColumnAssignments";
        $query = new Query( $sql, self::QUERY_CHANGE_ROWS, 'INSERT', $table );
        $this->query( $query, $fname );
        // Count updates of conflicting rows and row inserts equally toward the change count
        $this->lastQueryAffectedRows = min( $this->lastQueryAffectedRows, count( $rows ) );
    }
 
    public function replace( $table, $uniqueKeys, $rows, $fname = __METHOD__ ) {
        $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return;
        }
        $encTable = $this->tableName( $table );
        [ $sqlColumns, $sqlTuples ] = $this->platform->makeInsertLists( $rows );
        // https://dev.mysql.com/doc/refman/8.0/en/replace.html
        $sql = "REPLACE INTO $encTable ($sqlColumns) VALUES $sqlTuples";
        // Note that any auto-increment columns on conflicting rows will be reassigned
        // due to combined DELETE+INSERT semantics. This will be reflected in insertId().
        $query = new Query( $sql, self::QUERY_CHANGE_ROWS, 'REPLACE', $table );
        $this->query( $query, $fname );
        // Do not count deletions of conflicting rows toward the change count
        $this->lastQueryAffectedRows = min( $this->lastQueryAffectedRows, count( $rows ) );
    }
 
    public function wasDeadlock() {
        return $this->lastErrno() == 1213;
    }
 
    public function wasReadOnlyError() {
        return $this->lastErrno() == 1223 ||
            ( $this->lastErrno() == 1290 && strpos( $this->lastError(), '--read-only' ) !== false );
    }
 
    protected function isConnectionError( $errno ) {
        // https://mariadb.com/kb/en/mariadb-error-codes/
        // https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html
        // https://dev.mysql.com/doc/mysql-errors/8.0/en/client-error-reference.html
        return in_array( $errno, [ 2013, 2006, 2003, 1927, 1053 ], true );
    }
 
    protected function isQueryTimeoutError( $errno ) {
        // https://mariadb.com/kb/en/mariadb-error-codes/
        // https://dev.mysql.com/doc/refman/8.0/en/client-error-reference.html
        // https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html
        return in_array( $errno, [ 3024, 2062, 1969, 1028 ], true );
    }
 
    protected function isKnownStatementRollbackError( $errno ) {
        // https://mariadb.com/kb/en/mariadb-error-codes/
        // https://dev.mysql.com/doc/mysql-errors/8.0/en/server-error-reference.html
        return in_array(
            $errno,
            [ 3024, 1969, 1022, 1062, 1216, 1217, 1137, 1146, 1051, 1054 ],
            true
        );
    }
 
    public function duplicateTableStructure(
        $oldName, $newName, $temporary = false, $fname = __METHOD__
    ) {
        $tmp = $temporary ? 'TEMPORARY ' : '';
        $newNameQuoted = $this->addIdentifierQuotes( $newName );
        $oldNameQuoted = $this->addIdentifierQuotes( $oldName );
 
        $query = new Query(
            "CREATE $tmp TABLE $newNameQuoted (LIKE $oldNameQuoted)",
            self::QUERY_PSEUDO_PERMANENT | self::QUERY_CHANGE_SCHEMA,
            $temporary ? 'CREATE TEMPORARY' : 'CREATE',
            // Use a dot to avoid double-prefixing in Database::getTempTableWrites()
            '.' . $newName
        );
        return $this->query( $query, $fname );
    }
 
    public function listTables( $prefix = null, $fname = __METHOD__ ) {
        $qb = $this->newSelectQueryBuilder()
            ->select( 'table_name' )
            ->from( 'information_schema.tables' )
            ->where( [
                'table_schema' => $this->currentDomain->getDatabase(),
                'table_type' => 'BASE TABLE'
            ] )
            ->caller( $fname );
        if ( $prefix !== null && $prefix !== '' ) {
            $qb->andWhere( $this->expr(
                'table_name', IExpression::LIKE, new LikeValue( $prefix, $this->anyString() )
            ) );
        }
        return $qb->fetchFieldValues();
    }
 
    public function listViews( $prefix = null, $fname = __METHOD__ ) {
        wfDeprecated( __METHOD__, '1.42' );
        $qb = $this->newSelectQueryBuilder()
            ->select( 'table_name' )
            ->from( 'information_schema.views' )
            ->where( [ 'table_schema' => $this->currentDomain->getDatabase() ] )
            ->caller( $fname );
 
        if ( $prefix !== null && $prefix !== '' ) {
            $qb->andWhere( $this->expr(
                'table_name', IExpression::LIKE, new LikeValue( $prefix, $this->anyString() )
            ) );
        }
        return $qb->fetchFieldValues();
    }
 
    public function selectSQLText(
        $table,
        $vars,
        $conds = '',
        $fname = __METHOD__,
        $options = [],
        $join_conds = []
    ) {
        $sql = parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
        // https://dev.mysql.com/doc/refman/5.7/en/optimizer-hints.html
        // https://mariadb.com/kb/en/library/aborting-statements/
        $timeoutMsec = intval( $options['MAX_EXECUTION_TIME'] ?? 0 );
        if ( $timeoutMsec > 0 ) {
            [ $vendor, $number ] = $this->getMySqlServerVariant();
            if ( $vendor === 'MariaDB' && version_compare( $number, '10.1.2', '>=' ) ) {
                $timeoutSec = $timeoutMsec / 1000;
                $sql = "SET STATEMENT max_statement_time=$timeoutSec FOR $sql";
            } elseif ( $vendor === 'MySQL' && version_compare( $number, '5.7.0', '>=' ) ) {
                $sql = preg_replace(
                    '/^SELECT(?=\s)/',
                    "SELECT /*+ MAX_EXECUTION_TIME($timeoutMsec)*/",
                    $sql
                );
            }
        }
 
        return $sql;
    }
 
    protected function doSingleStatementQuery( string $sql ): QueryStatus {
        $conn = $this->getBindingHandle();
 
        // Hide packet warnings caused by things like dropped connections
        AtEase::suppressWarnings();
        $res = $conn->query( $sql );
        AtEase::restoreWarnings();
        // Note that mysqli::insert_id only reflects the last query statement
        $insertId = (int)$conn->insert_id;
        $this->lastQueryInsertId = $insertId;
        $this->sessionLastAutoRowId = $insertId ?: $this->sessionLastAutoRowId;
 
        return new QueryStatus(
            $res instanceof mysqli_result ? new MysqliResultWrapper( $this, $res ) : $res,
            $conn->affected_rows,
            $conn->error,
            $conn->errno
        );
    }
 
    private function mysqlConnect( $server, $user, $password, $db ) {
        if ( !function_exists( 'mysqli_init' ) ) {
            throw $this->newExceptionAfterConnectError(
                "MySQLi functions missing, have you compiled PHP with the --with-mysqli option?"
            );
        }
 
        // PHP 8.1.0+ throws exceptions by default. Turn that off for consistency.
        mysqli_report( MYSQLI_REPORT_OFF );
 
        // Other than mysql_connect, mysqli_real_connect expects an explicit port number
        // e.g. "localhost:1234" or "127.0.0.1:1234"
        // or Unix domain socket path
        // e.g. "localhost:/socket_path" or "localhost:/foo/bar:bar:bar"
        // colons are known to be used by Google AppEngine,
        // see <https://cloud.google.com/sql/docs/mysql/connect-app-engine>
        //
        // We need to parse the port or socket path out of $realServer
        $port = null;
        $socket = null;
        $hostAndPort = IPUtils::splitHostAndPort( $server );
        if ( $hostAndPort ) {
            $realServer = $hostAndPort[0];
            if ( $hostAndPort[1] ) {
                $port = $hostAndPort[1];
            }
        } elseif ( substr_count( $server, ':/' ) == 1 ) {
            // If we have a colon slash instead of a colon and a port number
            // after the ip or hostname, assume it's the Unix domain socket path
            [ $realServer, $socket ] = explode( ':', $server, 2 );
        } else {
            $realServer = $server;
        }
 
        $mysqli = mysqli_init();
        // Make affectedRows() for UPDATE reflect the number of matching rows, regardless
        // of whether any column values changed. This is what callers want to know and is
        // consistent with what Postgres and SQLite return.
        $flags = MYSQLI_CLIENT_FOUND_ROWS;
        if ( $this->ssl ) {
            $flags |= MYSQLI_CLIENT_SSL;
            $mysqli->ssl_set(
                $this->sslKeyPath,
                $this->sslCertPath,
                $this->sslCAFile,
                $this->sslCAPath,
                $this->sslCiphers
            );
        }
        if ( $this->getFlag( self::DBO_COMPRESS ) ) {
            $flags |= MYSQLI_CLIENT_COMPRESS;
        }
        if ( $this->getFlag( self::DBO_PERSISTENT ) ) {
            $realServer = 'p:' . $realServer;
        }
 
        if ( $this->utf8Mode ) {
            // Tell the server we're communicating with it in UTF-8.
            // This may engage various charset conversions.
            $mysqli->options( MYSQLI_SET_CHARSET_NAME, 'utf8' );
        } else {
            $mysqli->options( MYSQLI_SET_CHARSET_NAME, 'binary' );
        }
 
        $mysqli->options( MYSQLI_OPT_CONNECT_TIMEOUT, $this->connectTimeout ?: 3 );
        if ( $this->receiveTimeout ) {
            $mysqli->options( MYSQLI_OPT_READ_TIMEOUT, $this->receiveTimeout );
        }
 
        // @phan-suppress-next-line PhanTypeMismatchArgumentNullableInternal socket seems set when used
        $ok = $mysqli->real_connect( $realServer, $user, $password, $db, $port, $socket, $flags );
 
        return $ok ? $mysqli : null;
    }
 
    protected function closeConnection() {
        return ( $this->conn instanceof mysqli ) ? mysqli_close( $this->conn ) : true;
    }
 
    protected function lastInsertId() {
        return $this->sessionLastAutoRowId;
    }
 
    protected function doHandleSessionLossPreconnect() {
        // https://mariadb.com/kb/en/last_insert_id/
        $this->sessionLastAutoRowId = 0;
    }
 
    public function insertId() {
        if ( $this->lastEmulatedInsertId === null ) {
            $conn = $this->getBindingHandle();
            // Note that mysqli::insert_id only reflects the last query statement
            $this->lastEmulatedInsertId = (int)$conn->insert_id;
        }
 
        return $this->lastEmulatedInsertId;
    }
 
    public function lastErrno() {
        if ( $this->conn instanceof mysqli ) {
            return $this->conn->errno;
        } else {
            return mysqli_connect_errno();
        }
    }
 
    private function mysqlError( $conn = null ) {
        if ( $conn === null ) {
            return (string)mysqli_connect_error();
        } else {
            return $conn->error;
        }
    }
 
    private function mysqlRealEscapeString( $s ) {
        $conn = $this->getBindingHandle();
 
        return $conn->real_escape_string( (string)$s );
    }
}