lukecwik commented on code in PR #24025:
URL: https://github.com/apache/beam/pull/24025#discussion_r1035251386
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/FlatMapElements.java:
##########
@@ -45,16 +45,13 @@
extends PTransform<PCollection<? extends InputT>, PCollection<OutputT>> {
private final transient @Nullable TypeDescriptor<InputT> inputType;
private final transient @Nullable TypeDescriptor<OutputT> outputType;
- private final transient @Nullable Object originalFnForDisplayData;
- private final @Nullable Contextful<Fn<InputT, Iterable<OutputT>>> fn;
+ private final @Nullable Object fn;
private FlatMapElements(
- @Nullable Contextful<Fn<InputT, Iterable<OutputT>>> fn,
- @Nullable Object originalFnForDisplayData,
+ @Nullable Object fn,
Review Comment:
You're correct, the type system was too painful to specify `OR` between
`ProcessFunction` and `Contextful`.
Note that the constructor is private so this detail isn't exposed to users.
##########
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/FlatMapElements.java:
##########
@@ -137,57 +132,90 @@ public <NewInputT> FlatMapElements<NewInputT, OutputT>
via(
@Experimental(Kind.CONTEXTFUL)
public <NewInputT> FlatMapElements<NewInputT, OutputT> via(
Contextful<Fn<NewInputT, Iterable<OutputT>>> fn) {
- return new FlatMapElements<>(
- fn, fn.getClosure(), TypeDescriptors.inputOf(fn.getClosure()),
outputType);
+ return new FlatMapElements<>(fn, TypeDescriptors.inputOf(fn.getClosure()),
outputType);
}
@Override
public PCollection<OutputT> expand(PCollection<? extends InputT> input) {
checkArgument(fn != null, ".via() is required");
- return input.apply(
- "FlatMap",
- ParDo.of(
- new DoFn<InputT, OutputT>() {
- @ProcessElement
- public void processElement(ProcessContext c) throws
Exception {
- Iterable<OutputT> res =
- fn.getClosure().apply(c.element(),
Fn.Context.wrapProcessContext(c));
- for (OutputT output : res) {
- c.output(output);
+ if (fn instanceof Contextful) {
Review Comment:
Yes, half the cost of these trivial functions was going to creating and
destroying a Contextful that wraps a ProcessBundleDescriptor that is passed in.
Also note that the branch only happens during pipeline construction so it
won't show up on the execution side.
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