Hello, It seems that the ORC reader/writer support for attributes (in Arrow it is called metadata) is limited. The writer does not handle at all the writing of Arrow metadata (neither for the table nor for fields), and the reader fills the Arrow schema's metadata with the ORC file metadata, but does nothing for the fields' metadata, as far as I can tell looking at the code.
Looking at ORC, it seems that what they call "attributes" serves a similar purpose as Arrow metadata. See https://github.com/apache/orc/blob/ff6093c98bf38c06c906dde3207040e1b5b55753/c%2B%2B/include/orc/Type.hh#L50-L69 As the "Type" object can represent both the table and a particular field, I think that that could serve for passing the metadata. Is my understanding correct about the state of the ORC adapter and is there something that would prevent from doing that? Regards [https://opengraph.githubassets.com/d3ec807aa32290db4a737647fbcfced334e6375ead7cbbb1969b59be7db2cd43/apache/orc]<https://github.com/apache/orc/blob/ff6093c98bf38c06c906dde3207040e1b5b55753/c%2B%2B/include/orc/Type.hh#L50-L69> orc/Type.hh at ff6093c98bf38c06c906dde3207040e1b5b55753 · apache/orc<https://github.com/apache/orc/blob/ff6093c98bf38c06c906dde3207040e1b5b55753/c%2B%2B/include/orc/Type.hh#L50-L69> Apache ORC - the smallest, fastest columnar storage for Hadoop workloads - orc/Type.hh at ff6093c98bf38c06c906dde3207040e1b5b55753 · apache/orc github.com
