ProtoData contains the data rows and schema when constructing append
requests.
Attributes
rows
Serialized row data in protobuf message format.
Currently, the backend expects the serialized rows to adhere to
proto2 semantics when appending rows, particularly with respect to
how default values are encoded.
writerSchema
Proto schema used to serialize the data. This value only needs to be
provided as part of the first request on a gRPC network connection,
and will be ignored for subsequent requests on the connection.