This [1] appears to be the SQL layer on top of Arrow Flight specifically about SQL. It seems a bit chatty, where two network requests are required for each query if I read it correctly.
Yup. The chattiness is to account for distributed databases, so you can spread the result set across multiple instances.
That said there is a proposal for base Flight RPC to help allow embedding small results directly into the first response, that mostly needs someone to draft a prototype and push it through. (That doesn't help the case of a large-ish response from a single backend, though; that may also need some work, if we want to get rid of the second request.)
This [1] appears to be the SQL layer on top of Arrow Flight specifically about SQL. It seems a bit chatty, where two network requests are required for each query if I read it correctly.
[1] https://arrow.apache.org/docs/format/FlightSql.html