westonpace commented on a change in pull request #9095: URL: https://github.com/apache/arrow/pull/9095#discussion_r564809390
########## 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: What sort of optimization are you concerned about? Is it the std::function overhead? Because I agree, I don't think the compiler is going to optimize that away. This visitor is probably going to be called on a per-block basis and shouldn't really be used on a per-element basis. The overhead of calling the function is likely to be on par with the overhead already existing waiting for a future to complete, adding the callback, executing the callback, etc. ---------------------------------------------------------------- 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: us...@infra.apache.org
