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https://issues.apache.org/jira/browse/BEAM-3737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16507150#comment-16507150
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Debasish Das edited comment on BEAM-3737 at 6/9/18 8:21 PM:
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I saw this is being mentioned in TFMA
[https://github.com/tensorflow/model-analysis/blob/master/tensorflow_model_analysis/api/impl/evaluate.py]:_AggregateCombineFn...I
am not clear why BatchElements() is needed....groupByKey takes combiner which
should run on both map and reduce side...Am I missing something here ? Is it
the case that beam Combiner does not run on map side ? [~robertwb] is that why
you mentioned that we should run the combiner upfront in ParDo and then run
groupByKey to achieve map and reduce side combine ?
was (Author: debasish83):
I saw this is being mentioned in TFMA...I am also not clear why BatchElements()
is needed....groupByKey takes combiner which should run on both map and reduce
side...Am I missing something here ? Is it the case that beam Combiner does not
run on map side ? [~robertwb] is that why you mentioned that we should run the
combiner upfront in ParDo and then run groupByKey to achieve map and reduce
side combine ?
> Key-aware batching function
> ---------------------------
>
> Key: BEAM-3737
> URL: https://issues.apache.org/jira/browse/BEAM-3737
> Project: Beam
> Issue Type: New Feature
> Components: sdk-py-core
> Reporter: Chuan Yu Foo
> Priority: Major
>
> I have a CombineFn for which add_input has very large overhead. I would like
> to batch the incoming elements into a large batch before each call to
> add_input to reduce this overhead. In other words, I would like to do
> something like:
> {{elements | GroupByKey() | BatchElements() | CombineValues(MyCombineFn())}}
> Unfortunately, BatchElements is not key-aware, and can't be used after a
> GroupByKey to batch elements per key. I'm working around this by doing the
> batching within CombineValues, which makes the CombineFn rather messy. It
> would be nice if there were a key-aware BatchElements transform which could
> be used in this context.
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