westonpace commented on a change in pull request #9095:
URL: https://github.com/apache/arrow/pull/9095#discussion_r565956846
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File path: cpp/src/arrow/util/future.h
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@@ -556,6 +559,38 @@ inline bool WaitForAll(const std::vector<Future<T>*>&
futures,
return waiter->Wait(seconds);
}
+/// \brief Create a Future which completes when all of `futures` complete.
+///
+/// The future's result is a vector of the results of `futures`.
+/// Note that this future will never be marked "failed"; failed results
+/// will be stored in the result vector alongside successful results.
+template <typename T>
+Future<std::vector<Result<T>>> All(std::vector<Future<T>> futures) {
+ struct State {
+ explicit State(std::vector<Future<T>> f)
+ : futures(std::move(f)), n_remaining(futures.size()) {}
+
+ std::vector<Future<T>> futures;
+ std::atomic<size_t> n_remaining;
+ };
Review comment:
Ok. Yes, it could be done with the waiters if the waiter were given a
"finished future" and it marked it complete when the futures all finished.
Then a WaitForAllAsync could be added. I'm not sure there would be any
advantage though. The waiter is basically a named callback from the future's
perspective. I'm happy to proceed with this if you think it'll be cleaner.
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