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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-326) The lowest level map-reduce APIs should be byte oriented
Date Tue, 16 Feb 2010 19:41:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834405#action_12834405
] 

Owen O'Malley commented on MAPREDUCE-326:
-----------------------------------------

{quote}
If I understand the current proposal correctly, we could have a join where one mapper class
is pulling a big select statement from a DB, another is crunching some big compressed sequence
files, and another is pulling in a bunch of tiny Hive partitions using CombineFileInput, without
them stepping all over each other and creating "last one wins" configuration conditions. 
{quote}

Tom's current proposal doesn't address this at all. Please look at MAPREDUCE-1183, which actually
does.

I implemented the first version of pipes. I know what is required for this kind of framework.
Tom's proposal doesn't help at all. My proposal for a ByteBuffer-based MapContext write method
is necessary and *sufficient*.

> 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
>         Attachments: MAPREDUCE-326-api.patch, MAPREDUCE-326.pdf
>
>
> 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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