A simple key-value store w/persistent sqlite3 database.

sqlite_kv.dart

/// A simple key-value store w/persistent sqlite3 database.
class KV {
  KV._(this._db);
  final Database _db;

  static Future<KV> open(String name) async {
    return KV._(sqlite3.open(name)..execute('create table if not exists kv (k text primary key, v jsonb)'));
  }

  Future<Object?> get(String key) async {
    final value = _db.select('select * from kv where k=?', [key]).singleOrNull?.columnAt(1);
    return value == null ? null : json.decode(value);
  }

  Future<Object?> set(String key, Object? value) async {
    _db.execute('begin');
    try {
      final old = await get(key);
      if (value == null) {
        _db.execute('delete from kv where k=?', [key]);
      } else {
        _db.execute('insert or replace into kv (k,v) values (?,json(?))', [key, json.encode(value)]);
      }
      return old;
    } finally {
      _db.execute('commit');
    }
  }

  Stream<(String, Object?)> list(String prefix) async* {
    for (final row in _db.select('select * from kv where k like ?', ['$prefix%'])) {
      yield (row.columnAt(0), json.decode(row.columnAt(1)));
    }
  }

  Future<void> dispose() async => _db.dispose();
}