Struct arrow_flight::decode::FlightRecordBatchStream

pub struct FlightRecordBatchStream {
    headers: MetadataMap,
    trailers: Option<LazyTrailers>,
    inner: FlightDataDecoder,
}

Decodes a [Stream] of FlightData back into RecordBatches. This can be used to decode the response from an Arrow Flight server

Note

To access the lower level Flight messages (e.g. to access FlightData::app_metadata), you can call Self::into_inner and use the FlightDataDecoder directly.

Example:

// make a do_get request
use arrow_flight::{
  error::Result,
  decode::FlightRecordBatchStream,
  Ticket,
  flight_service_client::FlightServiceClient
};
use tonic::transport::Channel;
use futures::stream::{StreamExt, TryStreamExt};

let client: FlightServiceClient<Channel> = // make client..

let request = tonic::Request::new(
  Ticket { ticket: Bytes::new() }
);

// Get a stream of FlightData;
let flight_data_stream = client
  .do_get(request)
  .await?
  .into_inner();

// Decode stream of FlightData to RecordBatches
let record_batch_stream = FlightRecordBatchStream::new_from_flight_data(
  // convert tonic::Status to FlightError
  flight_data_stream.map_err(|e| e.into())
);

// Read back RecordBatches
while let Some(batch) = record_batch_stream.next().await {
  match batch {
    Ok(batch) => { /* process batch */ },
    Err(e) => { /* handle error */ },
  };
}

Fields

headers: MetadataMap

Optional grpc header metadata.

trailers: Option<LazyTrailers>

Optional grpc trailer metadata.

inner: FlightDataDecoder

Implementations

impl FlightRecordBatchStream

pub fn new(inner: FlightDataDecoder) -> Self

Create a new FlightRecordBatchStream from a decoded stream

pub fn new_from_flight_data<S>(inner: S) -> Self

where S: Stream<Item = Result<FlightData>> + Send + 'static,

Create a new FlightRecordBatchStream from a stream of FlightData

pub fn with_headers(self, headers: MetadataMap) -> Self

Record response headers.

pub fn with_trailers(self, trailers: LazyTrailers) -> Self

Record response trailers.

pub fn headers(&self) -> &MetadataMap

Headers attached to this stream.

pub fn trailers(&self) -> Option<MetadataMap>

Trailers attached to this stream.

Note that this will return None until the entire stream is consumed. Only after calling next() returns None, might any available trailers be returned.

pub fn got_schema(&self) -> bool

👎Deprecated: use schema().is_some() instead

Has a message defining the schema been received yet?

pub fn schema(&self) -> Option<&SchemaRef>

Return schema for the stream, if it has been received

pub fn into_inner(self) -> FlightDataDecoder

Consume self and return the wrapped FlightDataDecoder

Trait Implementations

impl Debug for FlightRecordBatchStream

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Stream for FlightRecordBatchStream

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_> ) -> Poll<Option<Result<RecordBatch>>>

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

type Item = Result<RecordBatch, FlightError>

Values yielded by the stream.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.