It's mostly a quirk of implementation (and just for clarification, they're all nearly identical on the format/protocol level).
DoGet is conceptualized as your application returning a readable stream of batches, instead of your application imperatively writing batches to the client. (This is different than how Flight is implemented in Java.) You would normally not implement FlightDataStream - you would return a RecordBatchStream. DoGet could not have FlightMessageWriter as a return type as that wouldn't make sense, but it could accept an instance of that as a parameter instead, much like DoExchange. That would be a breaking change. Best, David On Wed, Jun 23, 2021, at 08:47, Gosh Arzumanyan wrote: > Hi David, > > Going through the ArrowFlight API: got confused a bit on DoGet and > DoPut/DoExachange apis: the former one expects FlightDataStream which talks > in already serialized message terms while the latter to > accept FlightMessageReader/Writer which expect the user to pass in > RecordBatches etc. Is there any reason why the DoGet can't have > FlightMessageWriter as a return type? > > Cheers, > Gosh > > On Mon, Jun 21, 2021 at 9:47 PM Gosh Arzumanyan <gosh...@gmail.com> wrote: > > > Thanks David! > > > > I also responded/added more suggestions/questions to the doc. I think it > > makes sense to have two sections: one purely protocol oriented and second > > API oriented(examples in c++ or in any other language should make the idea > > easier to digest). > > > > Thanks for the reference too! > > > > Cheers, > > Gosh > > > > On Mon, Jun 21, 2021 at 4:41 PM David Li <lidav...@apache.org> wrote: > > > >> Thanks! I've left some initial comments/suggestions to expand it in terms > >> of the format definitions and not the C++ APIs. > >> > >> I'll also note something like this was proposed a long time ago - there's > >> not very much discussion about it there but for reference: > >> https://lists.apache.org/thread.html/0e5ba78c48cdd0e357f3a4a6d8affd31767c34376b62c001910823af%40%3Cdev.arrow.apache.org%3E > >> (or see the thread '[Discuss][FlightRPC] Extensions to Flight: > >> "DoBidirectional"' from 2019-2020). It might be good to address why the > >> proposed workaround there (union-of-structs) is insufficient for the use > >> cases here (and in FlightSQL). > >> > >> -David > >> > >> On Mon, Jun 21, 2021, at 08:22, Gosh Arzumanyan wrote: > >> > Ah sorry, comments should work now. > >> > > >> > Cheers, > >> > Gosh > >> > > >> > On Mon., 21 Jun. 2021, 14:18 David Li, <lidav...@apache.org <mailto: > >> lidavidm%40apache.org>> wrote: > >> > > >> > > Thanks! Will give it a look. > >> > > > >> > > Would you mind opening it up for comments? > >> > > > >> > > -David > >> > > > >> > > On 2021/06/21 11:56:24, Gosh Arzumanyan <gosh...@gmail.com <mailto: > >> gosharz%40gmail.com>> wrote: > >> > > > Hi folks, > >> > > > > >> > > > Started putting some thoughts together here: > >> > > > > >> > > > >> https://docs.google.com/document/d/1dIOpKNYwsd9sdChsRBAx37BiJXl_7enpwWkH76n1tOI/edit?usp=sharing > >> > > > Any feedback is welcome! > >> > > > > >> > > > Cheers, > >> > > > Gosh > >> > > > > >> > > > >> > > >> > > >
