pitrou commented on code in PR #34392:
URL: https://github.com/apache/arrow/pull/34392#discussion_r1196711606
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cpp/src/arrow/acero/asof_join_node.cc:
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@@ -239,24 +344,45 @@ struct MemoStore {
// the time of the current entry, defaulting to 0.
// when entries with a time less than T are removed, the current time is
updated to the
// time of the next (by-time) and now-current entry or to T if no such entry
exists.
- OnType current_time_;
+ std::atomic<OnType> current_time_;
// current entry per key
std::unordered_map<ByType, Entry> entries_;
// future entries per key
std::unordered_map<ByType, std::queue<Entry>> future_entries_;
// current and future (distinct) times of existing entries
std::deque<OnType> times_;
+#ifndef NDEBUG
+ // Owning node
+ AsofJoinNode* node_;
+ // Index of owning input
+ size_t index_;
+#endif
void swap(MemoStore& memo) {
+#ifndef NDEBUG
+ std::swap(node_, memo.node_);
+ std::swap(index_, memo.index_);
+#endif
std::swap(no_future_, memo.no_future_);
- std::swap(current_time_, memo.current_time_);
+ current_time_ =
memo.current_time_.exchange(static_cast<OnType>(current_time_));
entries_.swap(memo.entries_);
future_entries_.swap(memo.future_entries_);
times_.swap(memo.times_);
}
+ bool UpdateTime(OnType ts) {
+ OnType prev_time = current_time_;
+ bool update = prev_time < ts;
+ while (prev_time < ts && current_time_.compare_exchange_weak(prev_time,
ts)) {
+ // intentionally empty - standard CAS loop
Review Comment:
I'm not sure I understand. A standard CAS loop would retry when the CAS
operation fails, right? Here, it retries when the CAS succeeds...
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