suremarc commented on code in PR #4797:
URL: https://github.com/apache/arrow-rs/pull/4797#discussion_r1319945754
##########
arrow-flight/src/sql/server.rs:
##########
@@ -688,9 +688,17 @@ where
async fn do_put(
&self,
- mut request: Request<Streaming<FlightData>>,
+ request: Request<Streaming<FlightData>>,
) -> Result<Response<Self::DoPutStream>, Status> {
- let cmd = request.get_mut().message().await?.unwrap();
+ // See issue #4658: https://github.com/apache/arrow-rs/issues/4658
+ // To dispatch to the correct `do_put` method, we cannot discard the
first message,
+ // as it may contain the Arrow schema, which the `do_put` handler may
need.
+ // To allow the first message to be reused by the `do_put` handler,
+ // we wrap this stream in a `Peekable` one, which allows us to peek at
+ // the first message without discarding it.
+ let mut request = request.map(futures::StreamExt::peekable);
Review Comment:
Yes, that is my understanding as well. Prior to this change, decoding a
flight stream inside one of the `do_put` methods would give you an error like
`Received RecordBatch prior to schema`
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