Function GetFragmentsFromDatasets

cpp/src/arrow/dataset/dataset_internal.h:40–55

\brief GetFragmentsFromDatasets transforms a vector into a flattened FragmentIterator.

/// \brief GetFragmentsFromDatasets transforms a vector<Dataset> into a
/// flattened FragmentIterator.
inline Result<FragmentIterator> GetFragmentsFromDatasets(const DatasetVector& datasets,
                                                         compute::Expression predicate) {
  // Iterator<Dataset>
  auto datasets_it = MakeVectorIterator(datasets);

  // Dataset -> Iterator<Fragment>
  auto fn = [predicate](std::shared_ptr<Dataset> dataset) -> Result<FragmentIterator> {
    return dataset->GetFragments(predicate);
  };

  // Iterator<Iterator<Fragment>>
  auto fragments_it = MakeMaybeMapIterator(fn, std::move(datasets_it));

  // Iterator<Fragment>
  return MakeFlattenIterator(std::move(fragments_it));
}

inline std::shared_ptr<Schema> SchemaFromColumnNames(
    const std::shared_ptr<Schema>& input, const std::vector<std::string>& column_names) {