Method AppendRowGroups

cpp/src/parquet/metadata.cc:929–948

  }

  void AppendRowGroups(FileMetaDataImpl* other) {
    std::ostringstream diff_output;
    if (!schema()->Equals(*other->schema(), &diff_output)) {
      auto msg = "AppendRowGroups requires equal schemas.\n" + diff_output.str();
      throw ParquetException(msg);
    }

    // ARROW-13654: `other` may point to self, be careful not to enter an infinite loop
    const int n = other->num_row_groups();
    // ARROW-16613: do not use reserve() as that may suppress overallocation
    // and incur O(n²) behavior on repeated calls to AppendRowGroups().
    // (see https://en.cppreference.com/w/cpp/container/vector/reserve
    //  about inappropriate uses of reserve()).
    const auto start = metadata_->row_groups.size();
    metadata_->row_groups.resize(start + n);
    for (int i = 0; i < n; i++) {
      metadata_->row_groups[start + i] = other->row_group(i);
      metadata_->num_rows += metadata_->row_groups[start + i].num_rows;
    }
  }

  std::shared_ptr<FileMetaData> Subset(const std::vector<int>& row_groups) {
    for (int i : row_groups) {