Just a heads up - ballista has been donated to apache arrow, but they also broke the Rust arrow libraries into separate repos [0][1] in a break from the mono-repo model. Read more at the announcement[3] or the merge request[4].

[0] https://github.com/apache/arrow-datafusion

[1] https://github.com/apache/arrow-rs

[2] https://arrow.apache.org/blog/2021/05/04/rust-dev-workflow/

[3] https://github.com/apache/arrow/pull/10096