xinyuiscool commented on a change in pull request #14883:
URL: https://github.com/apache/beam/pull/14883#discussion_r640152071
##########
File path:
runners/samza/src/main/java/org/apache/beam/runners/samza/translation/ParDoBoundMultiTranslator.java
##########
@@ -368,6 +405,80 @@ public void translatePortable(
return Collections.emptyMap();
}
+ @SuppressWarnings("unchecked")
+ private static final ViewFn<Iterable<WindowedValue<?>>, ?> VIEW_FN =
+ (ViewFn)
+ new PCollectionViews.MultimapViewFn<>(
+
(PCollectionViews.TypeDescriptorSupplier<Iterable<WindowedValue<Void>>>)
+ () -> TypeDescriptors.iterables(new
TypeDescriptor<WindowedValue<Void>>() {}),
+ (PCollectionViews.TypeDescriptorSupplier<Void>)
TypeDescriptors::voids);
+
+ // This method follows the same way in Flink to create a runner-side Java
+ // PCollectionView to represent a portable side input.
+ private static PCollectionView<?> createPCollectionView(
+ SideInputId sideInputId,
+ WindowedValue.WindowedValueCoder<?> coder,
+ WindowingStrategy<?, BoundedWindow> windowingStrategy) {
+
+ return new RunnerPCollectionView<>(
+ null,
+ new TupleTag<>(sideInputId.getLocalName()),
+ VIEW_FN,
+ // TODO: support custom mapping fn
+ windowingStrategy.getWindowFn().getDefaultWindowMappingFn(),
+ windowingStrategy,
+ coder.getValueCoder());
+ }
+
+ // Group the side input globally with a null key and then broadcast it
+ // to all tasks.
+ private static <SideInputT>
+ MessageStream<OpMessage<Iterable<SideInputT>>>
groupAndBroadcastSideInput(
+ SideInputId sideInputId,
+ String sideInputCollectionId,
+ RunnerApi.PCollection sideInputPCollection,
+ WindowingStrategy<SideInputT, BoundedWindow> windowingStrategy,
+ WindowedValue.WindowedValueCoder<SideInputT> coder,
+ PortableTranslationContext ctx) {
+ final MessageStream<OpMessage<SideInputT>> sideInput =
+ ctx.getMessageStreamById(sideInputCollectionId);
+ final MessageStream<OpMessage<KV<Void, SideInputT>>> keyedSideInput =
+ sideInput.map(
+ opMessage -> {
+ WindowedValue<SideInputT> wv = opMessage.getElement();
+ return OpMessage.ofElement(wv.withValue(KV.of(null,
wv.getValue())));
Review comment:
Yup, null value is commonly used in beam to do global combine, as we do
it in java translation too. It's the same as placeholder, but I guess it's more
efficient (no key bytes).
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