Function MaybeConvertFieldRef

cpp/src/arrow/dataset/file_parquet.cc:284–302

Converts a field ref into a position-independent ref (containing only a sequence of names) based on the dataset schema. Returns `false` if no conversion was needed.

// Converts a field ref into a position-independent ref (containing only a sequence of
// names) based on the dataset schema. Returns `false` if no conversion was needed.
Result<FieldRef> MaybeConvertFieldRef(FieldRef ref, const Schema& dataset_schema) {
  if (ARROW_PREDICT_TRUE(ref.IsNameSequence())) {
    return ref;
  }

  ARROW_ASSIGN_OR_RAISE(auto path, ref.FindOne(dataset_schema));
  std::vector<FieldRef> named_refs;
  named_refs.reserve(path.indices().size());

  const FieldVector* child_fields = &dataset_schema.fields();
  for (auto index : path) {
    const auto& child_field = *(*child_fields)[index];
    named_refs.emplace_back(child_field.name());
    child_fields = &child_field.type()->fields();
  }

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

// Compute the column projection based on the scan options
Result<std::vector<int>> InferColumnProjection(const parquet::arrow::FileReader& reader,