+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 >
