mapleFU commented on code in PR #37514:
URL: https://github.com/apache/arrow/pull/37514#discussion_r1330188092
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cpp/src/arrow/dataset/file_parquet_test.cc:
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@@ -367,6 +369,69 @@ TEST_F(TestParquetFileFormat, MultithreadedScan) {
ASSERT_EQ(batches.size(), kNumRowGroups);
}
+class AsyncBufferReader : public ::arrow::io::BufferReader {
+ public:
+ explicit AsyncBufferReader(std::shared_ptr<Buffer> buffer,
+ const ::arrow::io::IOContext& ctx)
+ : ::arrow::io::BufferReader(std::move(buffer)), ctx_(ctx) {}
+ /// EXPERIMENTAL: Read data asynchronously.
+ Future<std::shared_ptr<Buffer>> ReadAsync(const ::arrow::io::IOContext& ctx,
+ int64_t position, int64_t nbytes)
override {
+ auto self = checked_pointer_cast<AsyncBufferReader>(shared_from_this());
+ return DeferNotOk(ctx.executor()->Submit(
+ [self, position, nbytes]() { return self->ReadAt(position, nbytes);
}));
+ }
+
+ const ::arrow::io::IOContext& io_context() const override { return ctx_; }
+
+ private:
+ ::arrow::io::IOContext ctx_;
+};
+
+TEST_F(TestParquetFileFormat, SingleThreadExecutor) {
+ ::arrow::io::IOContext default_io_context;
+ auto pool_executor =
+
dynamic_cast<::arrow::internal::ThreadPool*>(default_io_context.executor());
+ if (pool_executor == nullptr) {
+ GTEST_SKIP();
+ }
+ auto origin_capacity = pool_executor->GetCapacity();
+ ASSERT_OK(pool_executor->SetCapacity(/*threads=*/1));
+
+ // Reset capacity for pool_executor
+ struct PoolResetGuard {
+ PoolResetGuard(::arrow::internal::ThreadPool* pool, int origin_capacity)
+ : pool(pool), origin_capacity(origin_capacity) {}
+ ~PoolResetGuard() {
+ Status s = pool->SetCapacity(origin_capacity);
+ if (!s.ok()) {
+ std::cerr << "Failed to reset pool capacity: " << s.ToString() <<
std::endl;
+ }
+ }
+
+ ::arrow::internal::ThreadPool* pool;
+ int origin_capacity;
+ };
+ PoolResetGuard guard(pool_executor, origin_capacity);
Review Comment:
> I agree that it's odd BufferReader::ReadAsync and
MemoryMappedFile::ReadAsync (the only overrides I see) ignore the io context
argument
I think `BufferReader::ReadAsync` is so lightweight that we can ignore
ioContext?
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