paleolimbot commented on a change in pull request #12467: URL: https://github.com/apache/arrow/pull/12467#discussion_r831053629
########## File path: r/src/extension.cpp ########## @@ -0,0 +1,246 @@ +// 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. + +#include "./arrow_types.h" + +#if defined(ARROW_R_WITH_ARROW) + +#include <thread> + +#include <arrow/array.h> +#include <arrow/extension_type.h> +#include <arrow/type.h> + +// A wrapper around arrow::ExtensionType that allows R to register extension +// types whose Deserialize, ExtensionEquals, and Serialize methods are +// in meanintfully handled at the R level. At the C++ level, the type is +// already serialized to minimize calls to R from C++. +// +// Using a std::shared_ptr<> to wrap a cpp11::sexp type is unusual, but we +// need it here to avoid calling the copy constructor from another thread, +// since this might call into the R API. If we don't do this, we get crashes +// when reading a multi-file Dataset. +class RExtensionType : public arrow::ExtensionType { + public: + RExtensionType(const std::shared_ptr<arrow::DataType> storage_type, + std::string extension_name, std::string extension_metadata, + std::shared_ptr<cpp11::environment> r6_class, + std::thread::id creation_thread) + : arrow::ExtensionType(storage_type), + extension_name_(extension_name), + extension_metadata_(extension_metadata), + r6_class_(r6_class), + creation_thread_(creation_thread) {} + + std::string extension_name() const { return extension_name_; } + + bool ExtensionEquals(const arrow::ExtensionType& other) const; + + std::shared_ptr<arrow::Array> MakeArray(std::shared_ptr<arrow::ArrayData> data) const; + + arrow::Result<std::shared_ptr<arrow::DataType>> Deserialize( + std::shared_ptr<arrow::DataType> storage_type, + const std::string& serialized_data) const; + + std::string Serialize() const { return extension_metadata_; } + + std::string ToString() const; + + std::unique_ptr<RExtensionType> Clone() const; + + cpp11::environment r6_class() const { return *r6_class_; } + + cpp11::environment r6_instance(std::shared_ptr<arrow::DataType> storage_type, + const std::string& serialized_data) const; + + cpp11::environment r6_instance() const { + return r6_instance(storage_type(), Serialize()); + } + + private: + std::string extension_name_; + std::string extension_metadata_; + std::string cached_to_string_; + std::shared_ptr<cpp11::environment> r6_class_; + std::thread::id creation_thread_; + + arrow::Status assert_r_thread() const { + if (std::this_thread::get_id() == creation_thread_) { + return arrow::Status::OK(); + } else { + return arrow::Status::ExecutionError("RExtensionType <", extension_name_, + "> attempted to call into R ", + "from a non-R thread"); + } + } +}; + +bool RExtensionType::ExtensionEquals(const arrow::ExtensionType& other) const { + // Avoid materializing the R6 instance if at all possible, since this is slow + // and in some cases not possible due to threading + if (other.extension_name() != extension_name()) { + return false; + } + + if (other.Serialize() == Serialize()) { + return true; + } + + // With any ambiguity, we need to materialize the R6 instance and call its + // ExtensionEquals method. We can't do this on the non-R thread. + arrow::Status is_r_thread = assert_r_thread(); + if (!assert_r_thread().ok()) { + throw std::runtime_error(is_r_thread.message()); + } Review comment: This is another threading concern...the data types can't be checked for equality if the serialized data is not identical and the comparison occurs on another thread. I think this might happen when reading a multi-file dataset if some of the files were written differently. -- 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]
