HuaHuaY commented on code in PR #51328:
URL: https://github.com/apache/arrow/pull/51328#discussion_r4023649213
##########
cpp/src/arrow/util/cache_internal.h:
##########
@@ -167,42 +166,42 @@ struct ThreadUnsafeMemoizer {
};
template <template <typename...> class Cache, template <typename...> class
MemoizerType,
- typename Func, typename Key =
std::decay_t<call_traits::argument_type<0, Func>>,
- typename Value = std::decay_t<std::invoke_result_t<Func, const
Key&>>,
- typename Memoizer = MemoizerType<Key, Value, Cache<Key, Value>,
Func>,
- typename RetType = typename Memoizer::RetType>
-static std::function<RetType(const Key&)> Memoize(Func&& func, int32_t
cache_capacity) {
+ typename Key, typename Func>
+static auto Memoize(Func&& func, int32_t cache_capacity) {
+ using Value = std::decay_t<std::invoke_result_t<Func, const Key&>>;
+ using Memoizer = MemoizerType<Key, Value, Cache<Key, Value>, Func>;
+ using RetType = typename Memoizer::RetType;
+
// std::function<> requires copy constructibility
struct {
RetType operator()(const Key& key) const { return (*memoized_)(key); }
std::shared_ptr<Memoizer> memoized_;
} shared_memoized = {
std::make_shared<Memoizer>(std::forward<Func>(func), cache_capacity)};
- return shared_memoized;
+ return std::function<RetType(const Key&)>(std::move(shared_memoized));
Review Comment:
I previously copied and modified this file in iceberg-cpp repo. The file in
iceberg-cpp might be as pitrou described. Maybe we can open a new PR to
refactor the code.
https://github.com/apache/iceberg-cpp/pull/891/changes#diff-6e67f7ceb80cef4c07b66e68bc6907d481231abde46ce1168ed492eadbceb6f1
```cpp
template <template <typename...> class MemoizerType, typename Func>
auto Memoize(Func&& func, int32_t cache_capacity) {
using Function = decltype(std::function{std::forward<Func>(func)});
using Key = std::decay_t<typename unary_traits<Function>::arg>;
using Value = std::decay_t<std::invoke_result_t<Func, const Key&>>;
using Memoizer = MemoizerType<Key, Value, LruCache<Key, Value>, Func>;
return Memoizer(std::forward<Func>(func), cache_capacity);
}
// Apply a LRU memoization cache to a callable.
template <typename Func>
auto MemoizeLru(Func&& func, int32_t cache_capacity) {
return Memoize<ThreadSafeMemoizer>(std::forward<Func>(func),
cache_capacity);
}
```
However, I discovered that no code within Arrow currently uses this
`arrow::internal::LruCache`; perhaps we can simply delete the file.
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