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From "Gabriel Reid (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-286) ability to specify a different function for combiner & reducer
Date Fri, 25 Oct 2013 21:26:33 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13805713#comment-13805713
] 

Gabriel Reid commented on CRUNCH-286:
-------------------------------------

I don't think it's really necessary to make the in-memory impl replicate the MR impl -- it's
technically possible that an MR map-phase combiner wouldn't get any multiple values to combine,
so I think it's safe to just discard the map-phase CombineFn in the mem-pipeline impl. 

I'm thinking a mempipline doesn't execute a CombineFn in something like a map-phase anyway,
so it probably would make much of a difference there. Or would it?

> 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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