Method poll_next

arrow-flight/src/decode.rs:157–191

Returns the next [`RecordBatch`] available in this stream, or `None` if there are no further results available.

(
        mut self: Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    )

    /// Returns the next [`RecordBatch`] available in this stream, or `None` if
    /// there are no further results available.
    fn poll_next(
        mut self: Pin<&mut Self>,
        cx: &mut std::task::Context<'_>,
    ) -> Poll<Option<Result<RecordBatch>>> {
        loop {
            let had_schema = self.schema().is_some();
            let res = ready!(self.inner.poll_next_unpin(cx));
            match res {
                // Inner exhausted
                None => {
                    return Poll::Ready(None);
                }
                Some(Err(e)) => {
                    return Poll::Ready(Some(Err(e)));
                }
                // translate data
                Some(Ok(data)) => match data.payload {
                    DecodedPayload::Schema(_) if had_schema => {
                        return Poll::Ready(Some(Err(FlightError::protocol(
                            "Unexpectedly saw multiple Schema messages in FlightData stream",
                        ))));
                    }
                    DecodedPayload::Schema(_) => {
                        // Need next message, poll inner again
                    }
                    DecodedPayload::RecordBatch(batch) => {
                        return Poll::Ready(Some(Ok(batch)));
                    }
                    DecodedPayload::None => {
                        // Need next message
                    }
                },
            }
        }
    }
}

/// Wrapper around a stream of [`FlightData`] that handles the details