Transaction class final

A transaction proxy object for executing writes and reads atomically.

Obtained via Database.transaction. All operations use the writer connection, so reads see uncommitted writes from earlier statements in the same transaction.

Supports nested transactions via transaction, which uses SQLite SAVEPOINTs under the hood:

await db.transaction((tx) async {
  await tx.execute('INSERT INTO users(name) VALUES (?)', ['Ada']);

  // Nested transaction — uses SAVEPOINT internally.
  await tx.transaction((inner) async {
    await inner.execute('INSERT INTO users(name) VALUES (?)', ['Bob']);
    // Throw here to roll back only Bob's insert.
  });

  final rows = await tx.select('SELECT COUNT(*) as c FROM users');
  print(rows.first['c']); // includes Ada (and Bob if inner didn't throw)
});