The goal was to make schema transforms as efficient as hand-written coders. We found the avro encoding/decoding to often be quite inefficient, which is one reason we didn't use it for schemas.
Our schema encoding is internal to Beam though, and not suggested for use external to a pipeline. For sources or sinks we still recommend using Avro (or proto). On Thu, Jun 22, 2023 at 4:14 PM Robert Bradshaw <rober...@google.com> wrote: > On Thu, Jun 22, 2023 at 2:19 PM Ahmed Abualsaud <ahmedabuals...@google.com> > wrote: > >> Thank you all for your input. I have a PR for the changes I mentioned in >> my initial email: https://github.com/apache/beam/pull/27202. Please >> review when you get a chance! >> >> > perhaps we should consider just going to something Avro for portable >> coding rather than something custom >> >> Did you mean using some Avro object (GenericRecord?) besides Beam Row >> elements? We would still run into the problem Cham mentioned earlier (of >> making sure existing PTransform inputs/outputs are compatible with >> cross-language-valid types). >> > > I don't remember why Avro was rejected in favor of our own encoding > format, but it probably doesn't make sense to revisit that without > understanding the full history. I do know that avro versioning and diamond > dependencies cause a lot of pain for users and there's a concerted effort > to remove Avro from Beam core altogether. > > In any case, this is quite orthogonal to the proposal here which we should > move forward on. > > >> On Tue, May 30, 2023 at 10:53 PM Byron Ellis <byronel...@google.com> >> wrote: >> >>> Sure, I get that… though perhaps we should consider just going to >>> something Avro for portable coding rather than something custom. >>> >>> On Tue, May 30, 2023 at 2:22 PM Chamikara Jayalath <chamik...@google.com> >>> wrote: >>> >>>> 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 >>>>>>>>>> >>>>>>>>>
