presto-main/src/main/java/io/prestosql/execution/RollbackTask.java/RollbackTask/execute
class RollbackTask:    @Override
    public ListenableFuture<?> execute(Rollback statement, TransactionManager transactionManager, Metadata metadata, AccessControl accessControl, QueryStateMachine stateMachine, List<Expression> parameters)
    {
        Session session = stateMachine.getSession();
        if (!session.getTransactionId().isPresent()) {
            throw new PrestoException(NOT_IN_TRANSACTION, "No transaction in progress");
        }
        TransactionId transactionId = session.getTransactionId().get();

        stateMachine.clearTransactionId();
        transactionManager.asyncAbort(transactionId);
        return immediateFuture(null);
    }