JerAguilon commented on code in PR #38380: URL: https://github.com/apache/arrow/pull/38380#discussion_r1373704608
########## cpp/src/arrow/acero/concurrent_queue.h: ########## @@ -0,0 +1,150 @@ +// 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 <condition_variable> +#include <mutex> +#include <queue> +#include "arrow/acero/backpressure_handler.h" + +namespace arrow::acero { + +/** + * Simple implementation for an unbound concurrent queue + */ +template <class T> +class ConcurrentQueue { + public: + T Pop() { + std::unique_lock<std::mutex> lock(mutex_); + cond_.wait(lock, [&] { return !queue_.empty(); }); + return PopUnlocked(); + } + + T PopUnlocked() { + auto item = queue_.front(); + queue_.pop(); + return item; + } + + void Push(const T& item) { + std::unique_lock<std::mutex> lock(mutex_); + return PushUnlocked(item); + } + + void PushUnlocked(const T& item) { + queue_.push(item); + cond_.notify_one(); + } + + void Clear() { + std::unique_lock<std::mutex> lock(mutex_); + ClearUnlocked(); + } + + void ClearUnlocked() { queue_ = std::queue<T>(); } + + std::optional<T> TryPop() { + std::unique_lock<std::mutex> lock(mutex_); + return TryPopUnlocked(); + } + + std::optional<T> TryPopUnlocked() { + // Try to pop the oldest value from the queue (or return nullopt if none) + if (queue_.empty()) { + return std::nullopt; + } else { + auto item = queue_.front(); + queue_.pop(); + return item; + } + } + + bool Empty() const { + std::unique_lock<std::mutex> lock(mutex_); + return queue_.empty(); + } + + // Un-synchronized access to front + // For this to be "safe": + // 1) the caller logically guarantees that queue is not empty + // 2) pop/try_pop cannot be called concurrently with this + const T& UnsyncFront() const { return queue_.front(); } + + size_t UnsyncSize() const { return queue_.size(); } Review Comment: I'd like to leave these two around to limit the scope of this PR. I think it's a little hacky to be calling these but I'd need to put some thought about how to cleanly eradicate them from the asof join. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
