Input/output PCollection types at least have to be portable Beam types [1] for cross-language to work.
I think we restricted schema-aware transforms to PCollection<Row> since Row was expected to be an efficient replacement for arbitrary portable Beam types (not sure how true that is in practice currently). Thanks, Cham [1] https://github.com/apache/beam/blob/b9730952a7abf60437ee85ba2df6dd30556d6560/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto#L829 On Tue, May 30, 2023 at 1:54 PM Byron Ellis <byronel...@google.com> wrote: > Is it actually necessary for a PTransform that is configured via the > Schema mechanism to also be one that uses RowCoder? Those strike me as two > separate concerns and unnecessarily limiting. > > On Tue, May 30, 2023 at 1:29 PM Chamikara Jayalath <chamik...@google.com> > wrote: > >> +1 for the simplification. >> >> On Tue, May 30, 2023 at 12:33 PM Robert Bradshaw <rober...@google.com> >> wrote: >> >>> Yeah. Essentially one needs do (1) name the arguments and (2) implement >>> the transform. Hopefully (1) could be done in a concise way that allows for >>> easy consumption from both Java and cross-language. >>> >> >> +1 but I think the hard part today is to convert existing PTransforms to >> be schema-aware transform compatible (for example, change input/output >> types and make sure parameters take Beam Schema compatible types). But this >> makes sense for new transforms. >> >> >> >>> On Tue, May 30, 2023 at 12:25 PM Byron Ellis <byronel...@google.com> >>> wrote: >>> >>>> Or perhaps the other way around? If you have a Schema we can >>>> auto-generate the associated builder on the PTransform? Either way, more >>>> DRY. >>>> >>>> On Tue, May 30, 2023 at 10:59 AM Robert Bradshaw via dev < >>>> dev@beam.apache.org> wrote: >>>> >>>>> +1 to this simplification, it's a historical artifact that provides no >>>>> value. >>>>> >>>>> I would love it if we also looked into ways to auto-generate the >>>>> SchemaTransformProvider (e.g. via introspection if a transform takes a >>>>> small number of arguments, or uses the standard builder pattern...), >>>>> ideally with something as simple as adding a decorator to the PTransform >>>>> itself. >>>>> >>>>> >>>>> On Tue, May 30, 2023 at 7:42 AM Ahmed Abualsaud via dev < >>>>> dev@beam.apache.org> wrote: >>>>> >>>>>> Hey everyone, >>>>>> >>>>>> I was looking at how we use SchemaTransforms in our expansion >>>>>> service. From what I see, there may be a redundant step in developing >>>>>> SchemaTransforms. Currently, we have 3 pieces: >>>>>> - SchemaTransformProvider [1] >>>>>> - A configuration object >>>>>> - SchemaTransform [2] >>>>>> >>>>>> The API is generally used like this: >>>>>> 1. The SchemaTransformProvider takes a configuration object and >>>>>> returns a SchemaTransform >>>>>> 2. The SchemaTransform is used to build a PTransform according to the >>>>>> configuration >>>>>> >>>>>> In these steps, the SchemaTransform class seems unnecessary. We can >>>>>> combine the two steps if we have SchemaTransformProvider return the >>>>>> PTransform directly. >>>>>> >>>>>> We can then remove the SchemaTransform class as it will be obsolete. >>>>>> This should be safe to do; the only place it's used in our API is here >>>>>> [3], >>>>>> and that can be simplified if we make this change (we'd just trim ` >>>>>> .buildTransform()` off the end as `provider.from(configRow)` will >>>>>> directly return the PTransform). >>>>>> >>>>>> I'd like to first mention that I was not involved in the design >>>>>> process of this API so I may be missing some information on why it was >>>>>> set >>>>>> up this way. >>>>>> >>>>>> A few developers already raised questions about how there's seemingly >>>>>> unnecessary boilerplate involved in making a Java transform portable. I >>>>>> wasn't involved in the design process of this API so I may be missing >>>>>> some >>>>>> information, but my assumption is this was designed to follow the pattern >>>>>> of the previous iteration of this API (SchemaIO): SchemaIOProvider[4] -> >>>>>> SchemaIO[5] -> PTransform. However, with the newer >>>>>> SchemaTransformProvider API, we dropped a few methods and reduced the >>>>>> SchemaTransform class to have a generic buildTransform() method. See the >>>>>> example of PubsubReadSchemaTransformProvider [6], where the >>>>>> SchemaTransform interface and buildTransform method are implemented >>>>>> just to satisfy the requirement that SchemaTransformProvider::from >>>>>> return a SchemaTransform. >>>>>> >>>>>> I'm bringing this up because if we are looking to encourage >>>>>> contribution to cross-language use cases, we should make it simpler and >>>>>> less convoluted to develop portable transforms. >>>>>> >>>>>> There are a number of SchemaTransforms already developed, but >>>>>> applying these changes to them should be straightforward. If people think >>>>>> this is a good idea, I can open a PR and implement them. >>>>>> >>>>>> Best, >>>>>> Ahmed >>>>>> >>>>>> [1] >>>>>> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/SchemaTransformProvider.java >>>>>> [2] >>>>>> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/transforms/SchemaTransform.java >>>>>> [3] >>>>>> https://github.com/apache/beam/blob/d7ded3f07064919c202c81a2c786910e20a834f9/sdks/java/expansion-service/src/main/java/org/apache/beam/sdk/expansion/service/ExpansionServiceSchemaTransformProvider.java#L138 >>>>>> [4] >>>>>> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/io/SchemaIOProvider.java >>>>>> [5] >>>>>> https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/io/SchemaIO.java >>>>>> [6] >>>>>> https://github.com/apache/beam/blob/ed1a297904d5f5c743a6aca1a7648e3fb8f02e18/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsub/PubsubReadSchemaTransformProvider.java#L133-L137 >>>>>> >>>>>
