Method field

cpp/src/arrow/array/array_nested.cc:1087–1115

}

std::shared_ptr<Array> StructArray::field(int i) const {
  // Atomic ops on std::shared_ptr<T> are deprecated in C++20.  They should be
  // replaced with std::atomic<std::shared_ptr<T>> but not all C++ standard
  // libraries implement it yet. :-/
  ARROW_SUPPRESS_DEPRECATION_WARNING
  std::shared_ptr<Array> result = std::atomic_load(&impl_->boxed_fields_[i]);
  ARROW_UNSUPPRESS_DEPRECATION_WARNING
  if (result) {
    return result;
  }
  std::shared_ptr<ArrayData> field_data;
  if (data_->offset != 0 || data_->child_data[i]->length != data_->length) {
    field_data = data_->child_data[i]->Slice(data_->offset, data_->length);
  } else {
    field_data = data_->child_data[i];
  }
  result = MakeArray(field_data);
  // Check if some other thread inserted the array in the meantime and return
  // that in that case.
  std::shared_ptr<Array> expected = nullptr;
  ARROW_SUPPRESS_DEPRECATION_WARNING
  const bool update_successful =
      std::atomic_compare_exchange_strong(&impl_->boxed_fields_[i], &expected, result);
  ARROW_UNSUPPRESS_DEPRECATION_WARNING
  if (!update_successful) {
    result = std::move(expected);
  }
  return result;
}

std::shared_ptr<Array> StructArray::GetFieldByName(const std::string& name) const {
  int i = struct_type()->GetFieldIndex(name);