Function ToUniversalRef

cpp/src/arrow/dataset/file_json.cc:166–184

Converts a FieldPath to a FieldRef consisting exclusively of field names. The resulting FieldRef can be used to lookup the corresponding field in any schema regardless of missing/unordered fields. The input path is assumed to be valid for the given schema.

// regardless of missing/unordered fields. The input path is assumed to be valid for the
// given schema.
FieldRef ToUniversalRef(const FieldPath& path, const Schema& schema) {
  std::vector<FieldRef> refs;
  refs.reserve(path.indices().size());

  const FieldVector* fields = &schema.fields();
  for (auto it = path.begin(); it != path.end(); ++it) {
    DCHECK_LT(*it, static_cast<int>(fields->size()));
    const auto& child_field = *(*fields)[*it];
    refs.emplace_back(child_field.name());
    if (it + 1 != path.end()) {
      auto&& child_type = checked_cast<const StructType&>(*child_field.type());
      fields = &child_type.fields();
    }
  }

  return refs.empty()       ? FieldRef()
         : refs.size() == 1 ? refs[0]
                            : FieldRef(std::move(refs));
}

int TopLevelIndex(const FieldRef& ref, const Schema& schema) {
  if (const auto* name = ref.name()) {