westonpace commented on a change in pull request #9095: URL: https://github.com/apache/arrow/pull/9095#discussion_r565542380
########## File path: cpp/src/arrow/util/async_iterator.h ########## @@ -0,0 +1,295 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +#pragma once +#include <queue> + +#include "arrow/util/functional.h" +#include "arrow/util/future.h" +#include "arrow/util/iterator.h" +#include "arrow/util/optional.h" +#include "arrow/util/thread_pool.h" + +namespace arrow { + +template <typename T> +using AsyncGenerator = std::function<Future<T>()>; + +/// Iterates through a generator of futures, visiting the result of each one and +/// returning a future that completes when all have been visited +template <typename T> +Future<> VisitAsyncGenerator(AsyncGenerator<T> generator, + std::function<Status(T)> visitor) { Review comment: > (I'd also mention that std::function makes backtraces in debug mode rather annoying, but that's a much smaller concern) I can live with the backtraces (but I agree they are annoying) but it also makes it pretty much impossible to "step into" as well. Are you sure the overhead is std::function vs function pointer/lambda? I wonder how much optimization the compiler can really do with an arbitrary callable? For example, I've been bitten by lambda before when I captured an accumulator variable by reference because the accumulator, which had previously been a register, now required a full RAM write for every increment (since other threads could now conceivably be observing this). ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
