Delete web sqlite database from Dart

[davidmartos96]

Hello, I was wondering if it was possible to delete the database programatically on web. The same way you would do with the Chrome/Firefox devtools or with the Javascript API.

[simolus3]

Are you using package:drift/wasm.dart? That provides deleteDatabase, available through WasmDatabase.probe().

[davidmartos96]

Yes, I have this essentially, with a dart vm counter part.

import 'dart:async';

import 'package:drift/drift.dart';
import 'package:drift/wasm.dart';
import 'package:flutter/foundation.dart';

const webDbName = "todo-app";

/// Obtains a database connection for running drift on the web.
DatabaseConnection connect() {
  return DatabaseConnection.delayed(Future(() async {
    final db = await WasmDatabase.open(
      databaseName: webDbName,
      sqlite3Uri: Uri.parse('/sqlite3.wasm'),
      driftWorkerUri: Uri.parse('/drift_worker.js'),
    );

    if (db.missingFeatures.isNotEmpty) {
      debugPrint('Using ${db.chosenImplementation} due to unsupported '
          'browser features: ${db.missingFeatures}');
    }

    print("Chosen Web sqlite implementation: ${db.chosenImplementation}");

    return db.resolvedExecutor;
  }));
}

Future<void> deleteTodosDbFile() async {
  throw UnimplementedError();
}

[davidmartos96]

I've just tried the following, but it looks like the existingDatabases list is empty

Future<void> deleteTodosDbFile() async {
  final probeRes = await WasmDatabase.probe(
    sqlite3Uri: _sqlite3Uri,
    driftWorkerUri: _driftWorkerUri,
  );

  final db = _firstWhereOrNull(
    probeRes.existingDatabases,
    (dbInfo) => dbInfo.$2 == webDbName,
  );

  print(probeRes.existingDatabases);

  if (db != null) {
    await probeRes.deleteDatabase(db);
  }
}

[davidmartos96]

@simolus3 Found the problem, I wasn't providing the database name to probe. There is one additional issue, though.
The probeRes.deleteDatabase future never completes. From what I have researched, it is because for indexeddb, delete waits for all connections to close.
The problem is that even if drfitDb.close() is called, the shared worker still holds the native db connection. Is there any way to close it also in the worker?

[simolus3]

The problem is that even if drfitDb.close() is called, the shared worker still holds the native db connection. Is there any way to close it also in the worker?

I've implemented this in 09c6cf0, but it also requires a newer worker. It's not 100% reliable (if a second tab opens a database connection and gets closed, it can't tell the database server that the connection is dead). But the common case of opening a database, closing it and then deleting it should work.

[davidmartos96]

@simolus3 Thanks Simon, I will try it out next week. If I understood correctly, the limitation is that the worker is not able to detect when a tab closes, so it cannot tell when the number of clients reaches 0?

[simolus3]

Exactly, and I'm not aware of a good workaround for that. Perhaps we could send pings periodically but I'm not sure whether that's worth it.