Hi Igor, A workaround might be to send a single empty batch in the case of an empty stream.
I tried reproducing with PyArrow 10 but couldn't get it to crash. I filed ARROW-18320 [1] to look deeper. [1]: https://issues.apache.org/jira/browse/ARROW-18320 Thanks, David On Mon, Nov 14, 2022, at 07:18, Igor Seliverstov wrote: > Hi! > > I have an issue on my project, we have a query execution engine that returns > result data as a flight stream and c++ client that receives the stream. In > case a query has no results but the result schema implies dictionary encoded > fields in results we have client app crushed. > > The cause is in cpp/src/arrow/flight/client.cc:461: > > ::arrow::Result<std::unique_ptr<ipc::Message>> ReadNextMessage() override { > if (stream_finished_) { > return nullptr; > } > internal::FlightData* data; > { > auto guard = read_mutex_ ? std::unique_lock<std::mutex>(*read_mutex_) > : std::unique_lock<std::mutex>(); > peekable_reader_->Next(&data); > } > if (!data) { > stream_finished_ = true; > return stream_->Finish(Status::OK()); // Here the issue > } > // Validate IPC message > auto result = data->OpenMessage(); > if (!result.ok()) { > return stream_->Finish(std::move(result).status()); > } > *app_metadata_ = std::move(data->app_metadata); > return result; > } > > The method returns Result object while stream_Finish(..) returns a Status. So > there is an implicit conversion from Status to Result that causes > Result(Status) constructor to be called, but the constructor expects only > error statuses which in turn causes the app to be failed: > > /// Constructs a Result object with the given non-OK Status object. All > /// calls to ValueOrDie() on this object will abort. The given `status` must > /// not be an OK status, otherwise this constructor will abort. > /// > /// This constructor is not declared explicit so that a function with a return > /// type of `Result<T>` can return a Status object, and the status will be > /// implicitly converted to the appropriate return type as a matter of > /// convenience. > /// > /// \param status The non-OK Status object to initialize to. > Result(const Status& status) noexcept // NOLINT(runtime/explicit) > : status_(status) { > if (ARROW_PREDICT_FALSE(status.ok())) { > internal::DieWithMessage(std::string("Constructed with a non-error status: ") > + > status.ToString()); > } > } > > Is there a way to workaround or fix it? We use Arrow 6.0.0, but it seems that > the issue exists in all future versions. > > Regards, > Igor
