Tracing database operations

Drift provides the relatively simple logStatements option to print the statements it executes. The QueryInterceptor API can be used to extend this logging to provide more information, which this example will show.

class LogInterceptor extends QueryInterceptor {
  Future<T> _run<T>(
      String description, FutureOr<T> Function() operation) async {
    final stopwatch = Stopwatch()..start();
    print('Running $description');

    try {
      final result = await operation();
      print(' => succeeded after ${stopwatch.elapsedMilliseconds}ms');
      return result;
    } on Object catch (e) {
      print(' => failed after ${stopwatch.elapsedMilliseconds}ms ($e)');
      rethrow;
    }
  }

  @override
  TransactionExecutor beginTransaction(QueryExecutor parent) {
    print('begin');
    return super.beginTransaction(parent);
  }

  @override
  Future<void> commitTransaction(TransactionExecutor inner) {
    return _run('commit', () => inner.send());
  }

  @override
  Future<void> rollbackTransaction(TransactionExecutor inner) {
    return _run('rollback', () => inner.rollback());
  }

  @override
  Future<void> runBatched(
      QueryExecutor executor, BatchedStatements statements) {
    return _run(
        'batch with $statements', () => executor.runBatched(statements));
  }

  @override
  Future<int> runInsert(
      QueryExecutor executor, String statement, List<Object?> args) {
    return _run(
        '$statement with $args', () => executor.runInsert(statement, args));
  }

  @override
  Future<int> runUpdate(
      QueryExecutor executor, String statement, List<Object?> args) {
    return _run(
        '$statement with $args', () => executor.runUpdate(statement, args));
  }

  @override
  Future<int> runDelete(
      QueryExecutor executor, String statement, List<Object?> args) {
    return _run(
        '$statement with $args', () => executor.runDelete(statement, args));
  }

  @override
  Future<void> runCustom(
      QueryExecutor executor, String statement, List<Object?> args) {
    return _run(
        '$statement with $args', () => executor.runCustom(statement, args));
  }

  @override
  Future<List<Map<String, Object?>>> runSelect(
      QueryExecutor executor, String statement, List<Object?> args) {
    return _run(
        '$statement with $args', () => executor.runSelect(statement, args));
  }
}

Interceptors can be applied with the interceptWith extension on QueryExecutor and DatabaseConnection:

NativeDatabase.createInBackground(
  myDatabaseFile,
).interceptWith(LogInterceptor());

The QueryInterceptor class is pretty powerful, as it allows you to fully control the underlying database connection. You could also use it to retry some failing statements or to aggregate statistics about query times to an external monitoring service.