client parses schema from ipc batches

Author: andygrove

rust/arrow/src/ipc/reader.rs

@@ -29,6 +29,7 @@ use crate::compute::cast;
 use crate::datatypes::{DataType, IntervalUnit, Schema, SchemaRef};
 use crate::error::{ArrowError, Result};
 use crate::ipc;
+use crate::ipc::convert::fb_to_schema;
 use crate::record_batch::{RecordBatch, RecordBatchReader};
 use DataType::*;
 
@@ -663,6 +664,11 @@ impl<R: Read> RecordBatchReader for StreamReader<R> {
     }
 }
 
+pub fn schema_from_bytes(bytes: &[u8]) -> Option<Schema> {
+    let ipc = ipc::get_root_as_message(&bytes[..]);
+    ipc.header_as_schema().map(|schema| fb_to_schema(schema))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

rust/datafusion/examples/flight-client.rs

@@ -15,8 +15,8 @@
 // specific language governing permissions and limitations
 // under the License.
 
+use arrow::ipc::reader;
 use flight::flight_service_client::FlightServiceClient;
-
 use flight::Ticket;
 
 #[tokio::main]
@@ -31,6 +31,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     while let Some(batch) = stream.message().await? {
         println!("BATCH = {:?}", batch);
+
+        let schema = reader::schema_from_bytes(&batch.data_header);
+
+        println!("SCHEMA = {:?}", schema);
     }
 
     Ok(())