Hi, It just occurs to me that it may be a better idea to move the parquet module into a separate sub-crate by using cargo workspaces <https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html>. The advantage is that we can make the project more modular (in future, we may want to add more sub-crates such as arrow/parquet_derive, orc, gandiva, etc), and allow us to run CI jobs separately on each crate.
Some small caveats: 1. Cargo doesn't allow cyclic dependency. So if the parquet sub-crate depends on arrow, we can't reference parquet in arrow. This doesn't seem like an issue though since arrow itself should be physical on-disk format independent. I also didn't see any reference on parquet in cpp/src/arrow. 2. The path dependency used in workspace has to be changed to a version number when we do "cargo publish". This should be added to the release instructions and committer who performs the job should do the extra step. Thoughts? Chao
