[jira] [Commented] (BEAM-8732) Add support for additional structured types to Schemas/RowCoders

["Beam JIRA Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-8732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17169348#comment-17169348 ] 

Beam JIRA Bot commented on BEAM-8732:
-------------------------------------

This issue is P2 but has been unassigned without any comment for 60 days so it has been labeled "stale-P2". If this issue is still affecting you, we care! Please comment and remove the label. Otherwise, in 14 days the issue will be moved to P3.

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> Add support for additional structured types to Schemas/RowCoders
> ----------------------------------------------------------------
>
>                 Key: BEAM-8732
>                 URL: https://issues.apache.org/jira/browse/BEAM-8732
>             Project: Beam
>          Issue Type: New Feature
>          Components: sdk-py-core
>            Reporter: Chad Dombrova
>            Priority: P2
>              Labels: stale-P2
>
> Currently we can convert between a {{NamedTuple}} type and its {{Schema}} protos using {{named_tuple_from_schema}} and {{named_tuple_to_schema}}. I'd like to introduce a system to support additional types, starting with structured types like {{attrs}}, {{dataclasses}}, and {{TypedDict}}.
> I've only just started digesting the code, but this task seems pretty straightforward. For example, I think the type-to-schema code would look roughly like this:
> {code:python}
> def typing_to_runner_api(type_):
>   # type: (Type) -> schema_pb2.FieldType
>   structured_handler = _get_structured_handler(type_)
>   if structured_handler:
>     schema = None
>     if hasattr(type_, 'id'):
>       schema = SCHEMA_REGISTRY.get_schema_by_id(type_.id)
>     if schema is None:
>       fields = structured_handler.get_fields()
>       type_id = str(uuid4())
>       schema = schema_pb2.Schema(fields=fields, id=type_id)
>       SCHEMA_REGISTRY.add(type_, schema)
>     return schema_pb2.FieldType(
>         row_type=schema_pb2.RowType(
>             schema=schema))
> {code}
> The rest of the work would be in implementing a class hierarchy for working with structured types, such as getting a list of fields from an instance, and instantiation from a list of fields. Eventually we can extend this behavior to arbitrary, unstructured types.  
> Going in the schema-to-type direction, we have the problem of choosing which type to use for a given schema. I believe that as long as {{typing_to_runner_api()}} has been called on our structured type in the current python session, it should be added to the registry and thus round trip ok, so I think we just need a public function for registering schemas for structured types.
> [~bhulette] Did you want to tackle this or are you ok with me going after it?
>  



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