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https://issues.apache.org/jira/browse/BEAM-6740?focusedWorklogId=274296&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-274296
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ASF GitHub Bot logged work on BEAM-6740:
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Author: ASF GitHub Bot
Created on: 09/Jul/19 18:53
Start Date: 09/Jul/19 18:53
Worklog Time Spent: 10m
Work Description: youngoli commented on issue #8964: [BEAM-6740] Add
PTransformTranslator for Combine.Globally
URL: https://github.com/apache/beam/pull/8964#issuecomment-509763652
Yeah, the existing doc doesn't touch on `Combine.Globally` at all, but it's
essentially just `Combine.PerKey` with a global key. Once you've grouped all
elements under that global key I think you could just use
`COMBINE_GROUPED_VALUES`. (From what I remember combiner lifting isn't really
useful with a global combine but theoretically you could use the lifted version
of the expansion too.)
So I'd say a `Combine.Globally` can just expand to `GroupByGlobalKey` ->
`Combine.GroupedValues`, where `GroupByGlobalKey` is any transform that groups
all elements in an iterator under some arbitrary key. I don't know if a
transform like that exists in the Java SDK already, but it shouldn't be hard to
implement.
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Issue Time Tracking
-------------------
Worklog Id: (was: 274296)
Time Spent: 5h 20m (was: 5h 10m)
> Combine.Globally translation is never called
> --------------------------------------------
>
> Key: BEAM-6740
> URL: https://issues.apache.org/jira/browse/BEAM-6740
> Project: Beam
> Issue Type: Bug
> Components: runner-core
> Reporter: Etienne Chauchot
> Assignee: Ismaël Mejía
> Priority: Major
> Labels: portability
> Time Spent: 5h 20m
> Remaining Estimate: 0h
>
> Beam translates Combine.Globally as a composite transform composed of:
> * Map that assigns Void keys
> * Combine.PerKey
> on spark: As Combine.Perkey uses a spark GBK inside it, the runner adds its
> own translation of Combine.Globally to avoid less performant GBK. This
> translation should be called in place of entering the composite transform
> translation.A pipeline like this:
> {code:java}
> PCollection<Integer> input = pipeline.apply(Create.of(1, 2, 3, 4, 5, 6, 7, 8,
> 9, 10));
> input.apply(
> Combine.globally(new IntegerCombineFn()));
> {code}
> {code:java}
> private static class IntegerCombineFn extends Combine.CombineFn<Integer,
> Integer, Integer> {
> @Override
> public Integer createAccumulator() {
> return 0;
> }
> @Override
> public Integer addInput(Integer accumulator, Integer input) {
> return accumulator + input;
> }
> @Override
> public Integer mergeAccumulators(Iterable<Integer> accumulators) {
> Integer result = 0;
> for (Integer value : accumulators) {
> result += value;
> }
> return result;
> }
> @Override
> public Integer extractOutput(Integer accumulator) {
> return accumulator;
> }
> }
> {code}
> is translated as the above composite.
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