Class PoolResetGuard

cpp/src/arrow/dataset/file_parquet_test.cc:463–466

TEST_F(TestParquetFileFormat, SingleThreadExecutor) {
  // Reset capacity for io executor
  struct PoolResetGuard {
    int original_capacity = io::GetIOThreadPoolCapacity();
    ~PoolResetGuard() { DCHECK_OK(io::SetIOThreadPoolCapacity(original_capacity)); }
  } guard;
  ASSERT_OK(io::SetIOThreadPoolCapacity(1));

  auto reader = GetRecordBatchReader(schema({field("utf8", utf8())}));