robertwb commented on code in PR #17699:
URL: https://github.com/apache/beam/pull/17699#discussion_r876519616
##########
sdks/typescript/src/apache_beam/transforms/flatten.ts:
##########
@@ -22,23 +22,27 @@ import { PCollection } from "../pvalue";
import { Pipeline } from "../internal/pipeline";
import { GeneralObjectCoder } from "../coders/js_coders";
-export class Flatten<T> extends PTransform<PCollection<T>[], PCollection<T>> {
- // static urn: string =
runnerApi.StandardPTransforms_Primitives.GROUP_BY_KEY.urn;
- // TODO: (Cleanup) use above line, not below line.
- static urn: string = "beam:transform:flatten:v1";
- name = "Flatten";
-
- expandInternal(
+export function flatten<T>(): PTransform<PCollection<T>[], PCollection<T>> {
+ function expandInternal(
inputs: PCollection<T>[],
pipeline: Pipeline,
transformProto: runnerApi.PTransform
) {
transformProto.spec = runnerApi.FunctionSpec.create({
- urn: Flatten.urn,
+ urn: flatten.urn,
payload: null!,
});
- // TODO: Input coder if they're all the same? UnionCoder?
- return pipeline.createPCollectionInternal<T>(new GeneralObjectCoder());
+ // TODO: UnionCoder if they're not the same?
+ const coders = new Set(
+ inputs.map((pc) => pipeline.context.getPCollectionCoderId(pc))
+ );
+ const coder =
+ coders.size == 1 ? [...coders][0] : new GeneralObjectCoder<T>();
+ return pipeline.createPCollectionInternal<T>(coder);
}
+
+ return withName("flatten", expandInternal);
}
+
+flatten.urn = "beam:transform:flatten:v1";
Review Comment:
These URNs are defined in the proto files, but I wasn't sure how to extract
them out. This seemed the most natural place to stick it as a convention.
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