Support Arrow format in gRPC service

[waynexia]

Description

The query interface now supports avro and json format. https://github.com/CeresDB/ceresdb/blob/f6c9a5b03e23b04e6a06c4f73756f1be9551c0f8/server/src/grpc/query.rs#L42-L45 And avro is the only one actually used. Regardless of json, it's natural to support arrow (in arrow's ipc format) which is widely used in our server.

Proposal

Add support to arrow format. The execution result is RecordBatch so it wouldn't take a lot of effort to serialize it on the server side. Considering backward compatibility we can keep using avro as the default format, and client can require server to return a specific format it needs.

The protobuf is defined in https://github.com/CeresDB/ceresdbproto/blob/eba30f7dff736d00be711c40c3f01964655eb10a/protos/storage.proto#L101-L110

message QueryResponse {
  common.ResponseHeader header = 1;
  enum SchemaType {
    AVRO = 0;
    JSON = 1;
  }
  SchemaType schema_type = 2;
  string schema_content = 3;
  repeated bytes rows = 4;
}

It also might be necessary to do some renaming. Like SchemaType -> ResponseType, rows -> chunks etc.

Additional context

[Rachelint]

Maybe I can try it and make corresponding changes to rust client.

[ShiKaiWi]

This has been supported.