message: Union dataset fixes (OSX)
diff: @@ -316,7 +316,7 @@ struct UnionDataset::Itl
  vector<std::tuple<RowPath, CellValue> > res;
  for (int i = 0; i < datasets.size(); ++i) {
  const auto & d = datasets[i];
  - for (const auto curr: d->getColumnIndex()->getColumnValues(columnPath)) {
  + for (const auto & curr: d->getColumnIndex()->getColumnValues(columnPath)) {
  if (filter(std::get<1>(curr))) {
  res.emplace_back(
  PathElement(i) + std::get<0>(curr).toUtf8String().rawString(),
  @@ -327,7 +327,7 @@ struct UnionDataset::Itl
  return res;
  }
  - virtual size_t getRowCount() const
  + virtual uint64_t getRowCount() const
  {
  size_t count = 0;
  for (const auto & d: datasets) {
  