[GitHub] [arrow-rs] skejserjensen commented on issue #2445: `SchemaResult` in IPC deviates from other implementations

[GitBox <gi...@apache.org>]

skejserjensen commented on issue #2445:
URL: https://github.com/apache/arrow-rs/issues/2445#issuecomment-1225356558

   
   
   
   
   > You can change your server code to
   > 
   > ```
   > async fn get_schema(
   >     &self,
   >     _request: Request<FlightDescriptor>,
   > ) -> Result<Response<SchemaResult>, Status> {
   >     let tid = Field::new("tid", DataType::Int32, false);
   >     let timestamp = Field::new("timestamp", DataType::Timestamp(TimeUnit::Millisecond, None), false);
   >     let value = Field::new("value", DataType::Float32, false);
   >     let schema = Schema::new(vec![tid, timestamp, value]);
   > 
   >     let options = IpcWriteOptions::default();
   >     let schema_as_ipc = SchemaAsIpc::new(&schema, &options);
   >     // convert the schema as the ipc message
   >     let ipc_message : IpcMessage = IpcMessage::try_from(schema_as_ipc).unwrap();
   >     // wrap the `SchemaResult` using the ipc message bytes
   >     let schema_result: SchemaResult =  SchemaResult {
   >        schema: ipc_message.0,
   >     }
   > 
   >     Ok(Response::new(schema_result))
   > }
   > ```
   > 
   > @skejserjensen
   
   @liukun4515 and @zeroshade thank you for looking into this issue. 
   
   Based on @liukun4515's previous [comment](https://github.com/apache/arrow-rs/issues/2445#issuecomment-1223564637), I have also been looking into encoding [`Schema`](https://docs.rs/arrow/latest/arrow/datatypes/struct.Schema.html) as [`IpcMessage`](https://docs.rs/arrow-flight/latest/arrow_flight/struct.IpcMessage.html) using [`SchemaAsIpc`](https://docs.rs/arrow-flight/latest/arrow_flight/struct.SchemaAsIpc.html) and then returning the bytes from [`get_schema()`](https://docs.rs/arrow-flight/latest/arrow_flight/flight_service_server/trait.FlightService.html#tymethod.get_schema) as a  [`SchemaResult`](https://docs.rs/arrow-flight/latest/arrow_flight/struct.SchemaResult.html) to match the methods return type. I have successfully decoded these `SchemaResult`s containing the bytes from `IpcMessage`s using the Go, Java, Python, and Rust implementations of Apache Arrow Flight. 


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