When Using these sources or creating subclasses of them, you can provide a filter predicate and / or a set of fields (columns) to keep (project).
Same as TBaseRecordConverter with one important (subtle) difference.
The same as ParquetTBaseScheme, but sets the record convert to Parquet346TBaseRecordConverter
Takes a ThriftType with potentially missing structOrUnionType metadata, and makes a copy that sets all StructOrUnionType metadata to UNION