DatabaseSqlite.php

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<?php
namespace Wikimedia\Rdbms;
 
use FSLockManager;
use LockManager;
use NullLockManager;
use PDO;
use PDOException;
use PDOStatement;
use RuntimeException;
use Wikimedia\Rdbms\Platform\SqlitePlatform;
use Wikimedia\Rdbms\Platform\SQLPlatform;
use Wikimedia\Rdbms\Replication\ReplicationReporter;
 
class DatabaseSqlite extends Database {
    protected $dbDir;
    protected $dbPath;
    protected $trxMode;
 
    protected $conn;
 
    protected $lockMgr;
 
    private $version;
 
    private $sessionAttachedDbs = [];
 
    private const VALID_TRX_MODES = [ '', 'DEFERRED', 'IMMEDIATE', 'EXCLUSIVE' ];
 
    private const VALID_PRAGMAS = [
        // Optimizations or requirements regarding fsync() usage
        'synchronous' => [ 'EXTRA', 'FULL', 'NORMAL', 'OFF' ],
        // Optimizations for TEMPORARY tables
        'temp_store' => [ 'FILE', 'MEMORY' ],
        // Optimizations for disk use and page cache
        'mmap_size' => 'integer',
        // How many DB pages to keep in memory
        'cache_size' => 'integer',
    ];
 
    protected $platform;
 
    public function __construct( array $params ) {
        if ( isset( $params['dbFilePath'] ) ) {
            $this->dbPath = $params['dbFilePath'];
            if ( !isset( $params['dbname'] ) || $params['dbname'] === '' ) {
                $params['dbname'] = self::generateDatabaseName( $this->dbPath );
            }
        } elseif ( isset( $params['dbDirectory'] ) ) {
            $this->dbDir = $params['dbDirectory'];
        }
 
        parent::__construct( $params );
 
        $this->trxMode = strtoupper( $params['trxMode'] ?? '' );
 
        $this->lockMgr = $this->makeLockManager();
        $this->platform = new SqlitePlatform(
            $this,
            $this->logger,
            $this->currentDomain,
            $this->errorLogger
        );
        $this->replicationReporter = new ReplicationReporter(
            $params['topologyRole'],
            $this->logger,
            $params['srvCache']
        );
    }
 
    public static function getAttributes() {
        return [
            self::ATTR_DB_IS_FILE => true,
            self::ATTR_DB_LEVEL_LOCKING => true
        ];
    }
 
    public static function newStandaloneInstance( $filename, array $p = [] ) {
        $p['dbFilePath'] = $filename;
        $p['schema'] = null;
        $p['tablePrefix'] = '';
        $db = ( new DatabaseFactory() )->create( 'sqlite', $p );
        '@phan-var DatabaseSqlite $db';
 
        return $db;
    }
 
    public function getType() {
        return 'sqlite';
    }
 
    protected function open( $server, $user, $password, $db, $schema, $tablePrefix ) {
        $this->close( __METHOD__ );
 
        // Note that for SQLite, $server, $user, and $pass are ignored
 
        if ( $schema !== null ) {
            throw $this->newExceptionAfterConnectError( "Got schema '$schema'; not supported." );
        }
 
        if ( $this->dbPath !== null ) {
            $path = $this->dbPath;
        } elseif ( $this->dbDir !== null ) {
            $path = self::generateFileName( $this->dbDir, $db );
        } else {
            throw $this->newExceptionAfterConnectError( "DB path or directory required" );
        }
 
        // Check if the database file already exists but is non-readable
        if ( !self::isProcessMemoryPath( $path ) && is_file( $path ) && !is_readable( $path ) ) {
            throw $this->newExceptionAfterConnectError( 'SQLite database file is not readable' );
        } elseif ( !in_array( $this->trxMode, self::VALID_TRX_MODES, true ) ) {
            throw $this->newExceptionAfterConnectError( "Got mode '{$this->trxMode}' for BEGIN" );
        }
 
        $attributes = [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_SILENT,
            // Starting with PHP 8.1, The SQLite PDO returns proper types instead
            // of strings or null for everything. We cast every non-null value to
            // string to restore the old behavior.
            PDO::ATTR_STRINGIFY_FETCHES => true
        ];
        if ( $this->getFlag( self::DBO_PERSISTENT ) ) {
            // Persistent connections can avoid some schema index reading overhead.
            // On the other hand, they can cause horrible contention with DBO_TRX.
            if ( $this->getFlag( self::DBO_TRX ) || $this->getFlag( self::DBO_DEFAULT ) ) {
                $this->logger->warning(
                    __METHOD__ . ": ignoring DBO_PERSISTENT due to DBO_TRX or DBO_DEFAULT",
                    $this->getLogContext()
                );
            } else {
                $attributes[PDO::ATTR_PERSISTENT] = true;
            }
        }
 
        try {
            // Open the database file, creating it if it does not yet exist
            $this->conn = new PDO( "sqlite:$path", null, null, $attributes );
        } catch ( PDOException $e ) {
            throw $this->newExceptionAfterConnectError( $e->getMessage() );
        }
 
        $this->currentDomain = new DatabaseDomain( $db, null, $tablePrefix );
        $this->platform->setPrefix( $tablePrefix );
 
        try {
            // Enforce LIKE to be case sensitive, just like MySQL
            $query = new Query(
                'PRAGMA case_sensitive_like = 1',
                self::QUERY_CHANGE_TRX | self::QUERY_NO_RETRY,
                'PRAGMA'
            );
            $this->query( $query, __METHOD__ );
            // Set any connection-level custom PRAGMA options
            $pragmas = array_intersect_key( $this->connectionVariables, self::VALID_PRAGMAS );
            $pragmas += $this->getDefaultPragmas();
            foreach ( $pragmas as $name => $value ) {
                $allowed = self::VALID_PRAGMAS[$name];
                if (
                    ( is_array( $allowed ) && in_array( $value, $allowed, true ) ) ||
                    ( is_string( $allowed ) && gettype( $value ) === $allowed )
                ) {
                    $query = new Query(
                        "PRAGMA $name = $value",
                        self::QUERY_CHANGE_TRX | self::QUERY_NO_RETRY,
                        'PRAGMA',
                        null,
                        "PRAGMA $name = '?'"
                    );
                    $this->query( $query, __METHOD__ );
                }
            }
            $this->attachDatabasesFromTableAliases();
        } catch ( RuntimeException $e ) {
            throw $this->newExceptionAfterConnectError( $e->getMessage() );
        }
    }
 
    private function getDefaultPragmas() {
        $variables = [];
 
        if ( !$this->cliMode ) {
            $variables['temp_store'] = 'MEMORY';
        }
 
        return $variables;
    }
 
    public function getDbFilePath() {
        return $this->dbPath ?? self::generateFileName( $this->dbDir, $this->getDBname() );
    }
 
    public function getLockFileDirectory() {
        if ( $this->dbPath !== null && !self::isProcessMemoryPath( $this->dbPath ) ) {
            return dirname( $this->dbPath ) . '/locks';
        } elseif ( $this->dbDir !== null && !self::isProcessMemoryPath( $this->dbDir ) ) {
            return $this->dbDir . '/locks';
        }
 
        return null;
    }
 
    private function makeLockManager(): LockManager {
        $lockDirectory = $this->getLockFileDirectory();
        if ( $lockDirectory !== null ) {
            return new FSLockManager( [
                'domain' => $this->getDomainID(),
                'lockDirectory' => $lockDirectory,
            ] );
        } else {
            return new NullLockManager( [ 'domain' => $this->getDomainID() ] );
        }
    }
 
    protected function closeConnection() {
        $this->conn = null;
        // Release all locks, via FSLockManager::__destruct, as the base class expects
        $this->lockMgr = null;
 
        return true;
    }
 
    public static function generateFileName( $dir, $dbName ) {
        if ( $dir == '' ) {
            throw new DBUnexpectedError( null, __CLASS__ . ": no DB directory specified" );
        } elseif ( self::isProcessMemoryPath( $dir ) ) {
            throw new DBUnexpectedError(
                null,
                __CLASS__ . ": cannot use process memory directory '$dir'"
            );
        } elseif ( !strlen( $dbName ) ) {
            throw new DBUnexpectedError( null, __CLASS__ . ": no DB name specified" );
        }
 
        return "$dir/$dbName.sqlite";
    }
 
    private static function generateDatabaseName( $path ) {
        if ( preg_match( '/^(:memory:$|file::memory:)/', $path ) ) {
            // E.g. "file::memory:?cache=shared" => ":memory":
            return ':memory:';
        } elseif ( preg_match( '/^file::([^?]+)\?mode=memory(&|$)/', $path, $m ) ) {
            // E.g. "file:memdb1?mode=memory" => ":memdb1:"
            return ":{$m[1]}:";
        } else {
            // E.g. "/home/.../some_db.sqlite3" => "some_db"
            return preg_replace( '/\.sqlite\d?$/', '', basename( $path ) );
        }
    }
 
    private static function isProcessMemoryPath( $path ) {
        return preg_match( '/^(:memory:$|file:(:memory:|[^?]+\?mode=memory(&|$)))/', $path );
    }
 
    public static function getFulltextSearchModule() {
        static $cachedResult = null;
        if ( $cachedResult !== null ) {
            return $cachedResult;
        }
        $cachedResult = false;
        $table = 'dummy_search_test';
 
        $db = self::newStandaloneInstance( ':memory:' );
        if ( $db->query(
            "CREATE VIRTUAL TABLE $table USING FTS3(dummy_field)",
            __METHOD__,
            IDatabase::QUERY_SILENCE_ERRORS
        ) ) {
            $cachedResult = 'FTS3';
        }
        $db->close( __METHOD__ );
 
        return $cachedResult;
    }
 
    public function attachDatabase( $name, $file = false, $fname = __METHOD__ ) {
        $file = is_string( $file ) ? $file : self::generateFileName( $this->dbDir, $name );
        $encFile = $this->addQuotes( $file );
        $query = new Query(
            "ATTACH DATABASE $encFile AS $name",
            self::QUERY_CHANGE_TRX,
            'ATTACH'
        );
        return $this->query( $query, $fname );
    }
 
    protected function doSingleStatementQuery( string $sql ): QueryStatus {
        $res = $this->getBindingHandle()->query( $sql );
        // Note that rowCount() returns 0 for SELECT for SQLite
        return new QueryStatus(
            $res instanceof PDOStatement ? new SqliteResultWrapper( $res ) : $res,
            $res ? $res->rowCount() : 0,
            $this->lastError(),
            $this->lastErrno()
        );
    }
 
    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() ) {
            throw new DBExpectedError(
                $this,
                __CLASS__ . ": cannot change database (got '$database')"
            );
        }
 
        // Update that domain fields on success (no exception thrown)
        $this->currentDomain = $domain;
        $this->platform->setPrefix( $domain->getTablePrefix() );
 
        return true;
    }
 
    protected function lastInsertId() {
        // PDO::lastInsertId yields a string :(
        return (int)$this->getBindingHandle()->lastInsertId();
    }
 
    public function lastError() {
        if ( is_object( $this->conn ) ) {
            $e = $this->conn->errorInfo();
 
            return $e[2] ?? $this->lastConnectError;
        }
 
        return 'No database connection';
    }
 
    public function lastErrno() {
        if ( is_object( $this->conn ) ) {
            $info = $this->conn->errorInfo();
 
            if ( isset( $info[1] ) ) {
                return $info[1];
            }
        }
 
        return 0;
    }
 
    public function tableExists( $table, $fname = __METHOD__ ) {
        $tableRaw = $this->tableName( $table, 'raw' );
        if ( isset( $this->sessionTempTables[$tableRaw] ) ) {
            return true; // already known to exist
        }
 
        $encTable = $this->addQuotes( $tableRaw );
        $query = new Query(
            "SELECT 1 FROM sqlite_master WHERE type='table' AND name=$encTable",
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'SELECT'
        );
        $res = $this->query( $query, __METHOD__ );
 
        return (bool)$res->numRows();
    }
 
    public function indexInfo( $table, $index, $fname = __METHOD__ ) {
        $query = new Query(
            'PRAGMA index_info(' . $this->addQuotes( $this->platform->indexName( $index ) ) . ')',
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'PRAGMA'
        );
        $res = $this->query( $query, $fname );
        if ( !$res || $res->numRows() == 0 ) {
            return false;
        }
        $info = [];
        foreach ( $res as $row ) {
            $info[] = $row->name;
        }
 
        return $info;
    }
 
    public function indexUnique( $table, $index, $fname = __METHOD__ ) {
        $row = $this->selectRow( 'sqlite_master', '*',
            [
                'type' => 'index',
                'name' => $this->platform->indexName( $index ),
            ], $fname );
        if ( !$row || !isset( $row->sql ) ) {
            return null;
        }
 
        // $row->sql will be of the form CREATE [UNIQUE] INDEX ...
        $indexPos = strpos( $row->sql, 'INDEX' );
        if ( $indexPos === false ) {
            return null;
        }
        $firstPart = substr( $row->sql, 0, $indexPos );
        $options = explode( ' ', $firstPart );
 
        return in_array( 'UNIQUE', $options );
    }
 
    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://sqlite.org/lang_insert.html
        // 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(
            "REPLACE INTO $encTable ($sqlColumns) VALUES $sqlTuples",
            self::QUERY_CHANGE_ROWS,
            'REPLACE',
            $table
        );
        $this->query( $query, $fname );
    }
 
    public function textFieldSize( $table, $field ) {
        wfDeprecated( __METHOD__, '1.43' );
        return -1;
    }
 
    public function wasDeadlock() {
        return $this->lastErrno() == 5; // SQLITE_BUSY
    }
 
    public function wasReadOnlyError() {
        return $this->lastErrno() == 8; // SQLITE_READONLY;
    }
 
    protected function isConnectionError( $errno ) {
        return $errno == 17; // SQLITE_SCHEMA;
    }
 
    protected function isKnownStatementRollbackError( $errno ) {
        // ON CONFLICT ROLLBACK clauses make it so that SQLITE_CONSTRAINT error is
        // ambiguous with regard to whether it implies a ROLLBACK or an ABORT happened.
        // https://sqlite.org/lang_createtable.html#uniqueconst
        // https://sqlite.org/lang_conflict.html
        return false;
    }
 
    public function serverIsReadOnly() {
        $this->assertHasConnectionHandle();
 
        $path = $this->getDbFilePath();
 
        return ( !self::isProcessMemoryPath( $path ) && !is_writable( $path ) );
    }
 
    public function getSoftwareLink() {
        return "[{{int:version-db-sqlite-url}} SQLite]";
    }
 
    public function getServerVersion() {
        if ( $this->version === null ) {
            $this->version = $this->getBindingHandle()->getAttribute( PDO::ATTR_SERVER_VERSION );
        }
 
        return $this->version;
    }
 
    public function fieldInfo( $table, $field ) {
        $tableRaw = $this->tableName( $table, 'raw' );
        $query = new Query(
            'PRAGMA table_info(' . $this->addQuotes( $tableRaw ) . ')',
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'PRAGMA'
        );
        $res = $this->query( $query, __METHOD__ );
        foreach ( $res as $row ) {
            if ( $row->name == $field ) {
                return new SQLiteField( $row, $tableRaw );
            }
        }
 
        return false;
    }
 
    protected function doBegin( $fname = '' ) {
        if ( $this->trxMode != '' ) {
            $sql = "BEGIN {$this->trxMode}";
        } else {
            $sql = 'BEGIN';
        }
        $query = new Query( $sql, self::QUERY_CHANGE_TRX, 'BEGIN' );
        $this->query( $query, $fname );
    }
 
    public function strencode( $s ) {
        return substr( $this->addQuotes( $s ), 1, -1 );
    }
 
    public function encodeBlob( $b ) {
        return new Blob( $b );
    }
 
    public function decodeBlob( $b ) {
        if ( $b instanceof Blob ) {
            $b = $b->fetch();
        }
        if ( $b === null ) {
            // An empty blob is decoded as null in PHP before PHP 8.1.
            // It was probably fixed as a side-effect of caa710037e663fd78f67533b29611183090068b2
            $b = '';
        }
 
        return $b;
    }
 
    public function addQuotes( $s ) {
        if ( $s instanceof Blob ) {
            return "x'" . bin2hex( $s->fetch() ) . "'";
        } elseif ( is_bool( $s ) ) {
            return (string)(int)$s;
        } elseif ( is_int( $s ) ) {
            return (string)$s;
        } elseif ( strpos( (string)$s, "\0" ) !== false ) {
            // SQLite doesn't support \0 in strings, so use the hex representation as a workaround.
            // This is a known limitation of SQLite's mprintf function which PDO
            // should work around, but doesn't. I have reported this to php.net as bug #63419:
            // https://bugs.php.net/bug.php?id=63419
            // There was already a similar report for SQLite3::escapeString, bug #62361:
            // https://bugs.php.net/bug.php?id=62361
            // There is an additional bug regarding sorting this data after insert
            // on older versions of sqlite shipped with ubuntu 12.04
            // https://phabricator.wikimedia.org/T74367
            $this->logger->debug(
                __FUNCTION__ .
                ': Quoting value containing null byte. ' .
                'For consistency all binary data should have been ' .
                'first processed with self::encodeBlob()'
            );
            return "x'" . bin2hex( (string)$s ) . "'";
        } else {
            return $this->getBindingHandle()->quote( (string)$s );
        }
    }
 
    public function doLockIsFree( string $lockName, string $method ) {
        // Only locks by this thread will be checked
        return true;
    }
 
    public function doLock( string $lockName, string $method, int $timeout ) {
        $status = $this->lockMgr->lock( [ $lockName ], LockManager::LOCK_EX, $timeout );
        if (
            $this->lockMgr instanceof FSLockManager &&
            $status->hasMessage( 'lockmanager-fail-openlock' )
        ) {
            throw new DBError( $this, "Cannot create directory \"{$this->getLockFileDirectory()}\"" );
        }
 
        return $status->isOK() ? microtime( true ) : null;
    }
 
    public function doUnlock( string $lockName, string $method ) {
        return $this->lockMgr->unlock( [ $lockName ], LockManager::LOCK_EX )->isGood();
    }
 
    public function duplicateTableStructure(
        $oldName, $newName, $temporary = false, $fname = __METHOD__
    ) {
        $query = new Query(
            "SELECT sql FROM sqlite_master WHERE tbl_name=" .
            $this->addQuotes( $oldName ) . " AND type='table'",
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'SELECT'
        );
        $res = $this->query( $query, $fname );
        $obj = $res->fetchObject();
        if ( !$obj ) {
            throw new RuntimeException( "Couldn't retrieve structure for table $oldName" );
        }
        $sqlCreateTable = $obj->sql;
        $sqlCreateTable = preg_replace(
            '/(?<=\W)"?' .
                preg_quote( trim( $this->platform->addIdentifierQuotes( $oldName ), '"' ), '/' ) .
                '"?(?=\W)/',
            $this->platform->addIdentifierQuotes( $newName ),
            $sqlCreateTable,
            1
        );
        $flags = self::QUERY_CHANGE_SCHEMA | self::QUERY_PSEUDO_PERMANENT;
        if ( $temporary ) {
            if ( preg_match( '/^\\s*CREATE\\s+VIRTUAL\\s+TABLE\b/i', $sqlCreateTable ) ) {
                $this->logger->debug(
                    "Table $oldName is virtual, can't create a temporary duplicate." );
            } else {
                $sqlCreateTable = str_replace(
                    'CREATE TABLE',
                    'CREATE TEMPORARY TABLE',
                    $sqlCreateTable
                );
            }
        }
 
        $query = new Query(
            $sqlCreateTable,
            $flags,
            $temporary ? 'CREATE TEMPORARY' : 'CREATE',
            // Use a dot to avoid double-prefixing in Database::getTempTableWrites()
            '.' . $newName
        );
        $res = $this->query( $query, $fname );
 
        $query = new Query(
            'PRAGMA INDEX_LIST(' . $this->addQuotes( $oldName ) . ')',
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'PRAGMA'
        );
        // Take over indexes
        $indexList = $this->query( $query, $fname );
        foreach ( $indexList as $index ) {
            if ( strpos( $index->name, 'sqlite_autoindex' ) === 0 ) {
                continue;
            }
 
            if ( $index->unique ) {
                $sqlIndex = 'CREATE UNIQUE INDEX';
            } else {
                $sqlIndex = 'CREATE INDEX';
            }
            // Try to come up with a new index name, given indexes have database scope in SQLite
            $indexName = $newName . '_' . $index->name;
            $sqlIndex .= ' ' . $this->platform->addIdentifierQuotes( $indexName ) .
                ' ON ' . $this->platform->addIdentifierQuotes( $newName );
 
            $query = new Query(
                'PRAGMA INDEX_INFO(' . $this->addQuotes( $index->name ) . ')',
                self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
                'PRAGMA'
            );
            $indexInfo = $this->query( $query, $fname );
            $fields = [];
            foreach ( $indexInfo as $indexInfoRow ) {
                $fields[$indexInfoRow->seqno] = $this->addQuotes( $indexInfoRow->name );
            }
 
            $sqlIndex .= '(' . implode( ',', $fields ) . ')';
 
            $query = new Query(
                $sqlIndex,
                self::QUERY_CHANGE_SCHEMA | self::QUERY_PSEUDO_PERMANENT,
                'CREATE',
                $newName
            );
            $this->query( $query, __METHOD__ );
        }
 
        return $res;
    }
 
    public function listTables( $prefix = null, $fname = __METHOD__ ) {
        $query = new Query(
            "SELECT name FROM sqlite_master WHERE type = 'table'",
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'SELECT'
        );
        $result = $this->query( $query, $fname );
 
        $endArray = [];
 
        foreach ( $result as $table ) {
            $vars = get_object_vars( $table );
            $table = array_pop( $vars );
 
            if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
                if ( strpos( $table, 'sqlite_' ) !== 0 ) {
                    $endArray[] = $table;
                }
            }
        }
 
        return $endArray;
    }
 
    public function truncateTable( $table, $fname = __METHOD__ ) {
        $this->startAtomic( $fname );
        // Use "truncate" optimization; https://www.sqlite.org/lang_delete.html
        $query = new Query(
            "DELETE FROM " . $this->tableName( $table ),
            self::QUERY_CHANGE_SCHEMA,
            'DELETE',
            $table
        );
        $this->query( $query, $fname );
 
        $encMasterTable = $this->platform->addIdentifierQuotes( 'sqlite_sequence' );
        $encSequenceName = $this->addQuotes( $this->tableName( $table, 'raw' ) );
        $query = new Query(
            "DELETE FROM $encMasterTable WHERE name = $encSequenceName",
            self::QUERY_CHANGE_SCHEMA,
            'DELETE',
            'sqlite_sequence'
        );
        $this->query( $query, $fname );
 
        $this->endAtomic( $fname );
    }
 
    public function setTableAliases( array $aliases ) {
        parent::setTableAliases( $aliases );
        if ( $this->isOpen() ) {
            $this->attachDatabasesFromTableAliases();
        }
    }
 
    private function attachDatabasesFromTableAliases() {
        foreach ( $this->platform->getTableAliases() as $params ) {
            if (
                $params['dbname'] !== $this->getDBname() &&
                !isset( $this->sessionAttachedDbs[$params['dbname']] )
            ) {
                $this->attachDatabase( $params['dbname'], false, __METHOD__ );
                $this->sessionAttachedDbs[$params['dbname']] = true;
            }
        }
    }
 
    public function databasesAreIndependent() {
        return true;
    }
 
    protected function doHandleSessionLossPreconnect() {
        $this->sessionAttachedDbs = [];
        // Release all locks, via FSLockManager::__destruct, as the base class expects;
        $this->lockMgr = null;
        // Create a new lock manager instance
        $this->lockMgr = $this->makeLockManager();
    }
 
    protected function doFlushSession( $fname ) {
        // Release all locks, via FSLockManager::__destruct, as the base class expects
        $this->lockMgr = null;
        // Create a new lock manager instance
        $this->lockMgr = $this->makeLockManager();
    }
 
    protected function getBindingHandle() {
        return parent::getBindingHandle();
    }
 
    protected function getInsertIdColumnForUpsert( $table ) {
        $tableRaw = $this->tableName( $table, 'raw' );
        $query = new Query(
            'PRAGMA table_info(' . $this->addQuotes( $tableRaw ) . ')',
            self::QUERY_IGNORE_DBO_TRX | self::QUERY_CHANGE_NONE,
            'PRAGMA'
        );
        $res = $this->query( $query, __METHOD__ );
        foreach ( $res as $row ) {
            if ( $row->pk && strtolower( $row->type ) === 'integer' ) {
                return $row->name;
            }
        }
 
        return null;
    }
}