Multiple databases in a single isolate

[Airyzz]

Hi, I am developing an application which needs to store data in multiple different instances of a database to handle multiple accounts, sometimes accessing both databases simultaneously.

Currently, I have one isolate per database, but I am wondering if it is possible to just use a single isolate, with all databases on the same isolate?

thanks!

[simolus3]

Currently, I have one isolate per database, but I am wondering if it is possible to just use a single isolate, with all databases on the same isolate?

This is what I came up with. It uses unreleased drift APIs to cleanup unused servers, you'd have to remove the beforeShutdown and shutdownAfterLastDisconnect parameters before drift 2.20 is out (hopefully soon):

final class MultiDatabaseServer {
  final Map<String, DriftIsolate> _activeIsolates = {};
  final ReceivePort _receiveConnections = ReceivePort();

  MultiDatabaseServer() {
    _receiveConnections.listen((message) {
      if (message is (String, SendPort)) {
        final name = message.$1;
        final isolate = _activeIsolates.putIfAbsent(
          name,
          () {
            return DriftIsolate.inCurrent(
              // obviously you can pass a path instead of a name and use that to open the right NativeDatabase
              () => NativeDatabase.memory(
                  setup: (db) => db.createFunction(
                        functionName: 'db_name',
                        function: (args) => name,
                      )),
              beforeShutdown: () {
                _activeIsolates.remove(name);
              },
              shutdownAfterLastDisconnect: true,
            );
          },
        );

        message.$2.send(isolate.connectPort);
      }
    });
  }
}

Future<DatabaseConnection> connect(SendPort port, String databaseName) async {
  final response = ReceivePort();
  port.send((databaseName, response.sendPort));

  final connectPort = await response.first as SendPort;
  return DriftIsolate.fromConnectPort(connectPort, serialize: false).connect();
}

You can then use this to connect different databases to that isolate (Database here is a @DriftDatabase class):

Future<void> main() async {
  final receiveConnectPort = ReceivePort();
  Isolate.spawn((SendPort port) {
    final server = MultiDatabaseServer();
    port.send(server._receiveConnections.sendPort);
  }, receiveConnectPort.sendPort);
  final connectToServer = await receiveConnectPort.first as SendPort;

  final db1 = Database(await connect(connectToServer, 'one'));
  final db2 = Database(await connect(connectToServer, 'two'));

  print((await db1.customSelect('SELECT db_name()').getSingle()).data);
  print((await db2.customSelect('SELECT db_name()').getSingle()).data);
}

[Airyzz]

Works like a charm! thanks!