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https://issues.apache.org/jira/browse/CRUNCH-286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13805725#comment-13805725
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Josh Wills commented on CRUNCH-286:
-----------------------------------
So you mean treat the map-side phase for the mem pipeline as if there was
exactly one observation per? But that one observation would still be processed
by the combiner, so like if the combiner did something like take the values,
sum them, and add 17 to the result, I think that logic would get executed
twice-- once in the combiner and once in the reducer. That seems like a bad
example, now that I look at it-- there may be a more intelligent one that has a
similar issue. :)
> ability to specify a different function for combiner & reducer
> --------------------------------------------------------------
>
> Key: CRUNCH-286
> URL: https://issues.apache.org/jira/browse/CRUNCH-286
> Project: Crunch
> Issue Type: New Feature
> Components: Core
> Reporter: Stefan De Smit
> Assignee: Josh Wills
> Priority: Minor
> Attachments:
> 0001-add-combineValues-method-with-2-function-arguments.patch, 0002-.patch,
> CRUNCH-286-prototype.patch
>
>
> Extend PGroupedTable with an extra combineValues function that accepts 2
> functions: 1 for combiner phase, 1 for reducer phase.
> This way, different algorithm can be applied.
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