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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-326) The lowest level map-reduce APIs should be byte oriented
Date Thu, 04 Feb 2010 19:16:29 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12829710#action_12829710
] 

Doug Cutting commented on MAPREDUCE-326:
----------------------------------------

Todd> If you want to actually look at the data, it doesn't really help much.

Good point.  So maybe Java would take a performance hit.  But the data wouldn't need to deserialized.
 We'd need to compare it a few times.  Ah, the rub.  Unless we mandate Avro compare and/or
strcmp, comparison needs to be done in user code.  Sigh.

Todd> Is the assumption also that the InputFormat would run entirely in the child process
[ ... ]?

Yes.

Todd> How do we turn a dbinputformat split into a bytebuffer if the inputformat lives on
the child side?

The bytebuffer could contain the query.  The child could execute that query.


> The lowest level map-reduce APIs should be byte oriented
> --------------------------------------------------------
>
>                 Key: MAPREDUCE-326
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-326
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>            Reporter: eric baldeschwieler
>
> As discussed here:
> https://issues.apache.org/jira/browse/HADOOP-1986#action_12551237
> The templates, serializers and other complexities that allow map-reduce to use arbitrary
types complicate the design and lead to lots of object creates and other overhead that a byte
oriented design would not suffer.  I believe the lowest level implementation of hadoop map-reduce
should have byte string oriented APIs (for keys and values).  This API would be more performant,
simpler and more easily cross language.
> The existing API could be maintained as a thin layer on top of the leaner API.

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