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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-326) The lowest level map-reduce APIs should be byte oriented
Date Sat, 13 Feb 2010 01:29:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833276#action_12833276

Tom White commented on MAPREDUCE-326:

bq. That is completely untrue. It is mark unstable as a warning to users. I would reject any
incompatible change to the API. We should mark the base classes (Mapper, Reducer, InputFormat,
OutputFormat, Partitioner, RecordReader, RecordWriter, Partitioner, *Context) as stable. Pig
is already using the new APIs and so are a lot of other business critical applications.

Sorry, there must some misunderstanding here. I meant the *low-level* API is marked "unstable".
The existing MapReduce APIs can and should be marked as "stable". To be clear: this proposal
does not change these APIs (Goal 2 in the document).

bq. But it is the primary interface that our users use. If you are proposing that we make
this the "real" interface, then I've already expressed my -1. Users don't want to think in

Again, I seem to have expressed myself unclearly, and I apologize if that's the case. I am
not proposing that we make the low-level API a user-level interface. I agree that users don't
want to think in bytes, but this proposal doesn't expect them to. Users would use the same
object-based MapReduce API they use today, oblivious to the existence of a raw, low-level

> 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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