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From "Dave Beech (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-132) Repeated runs result in duplicated output data
Date Thu, 13 Dec 2012 20:24:12 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13531439#comment-13531439
] 

Dave Beech commented on CRUNCH-132:
-----------------------------------

+1 for Gabriel's suggestion. I've thought about it some more since opening the JIRA and although
it was confusing at first, I can see how it would be useful. Being able to choose between
those 3 behaviours would be perfect. And if somebody could just add that feature into Hadoop
at the same time, that'd be even better ;)

I don't know enough about the code yet to suggest a good place to implement something like
this, so for now I'll leave that for you guys to figure out.   
                
> Repeated runs result in duplicated output data
> ----------------------------------------------
>
>                 Key: CRUNCH-132
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-132
>             Project: Crunch
>          Issue Type: Bug
>    Affects Versions: 0.4.0
>            Reporter: Dave Beech
>
> Usually when you run a mapreduce job and the output directory already exists, the job
fails (won't start). A Crunch job does run, but results in the output data being duplicated
in the output directory with numbered files that follow on from the previous run. 
> Example
> Run 1, single reducer /output -> /output/part-r-00000
> Run 2, single reducer /output -> /output/part-r-00000, /output/part-r-00001
> I didn't realise I'd run my job twice, so when I looked in the directory it seemed that
there had been 2 reducers and somehow the output had been generated twice, which was confusing.

> I realise this may be by design, but it feels wrong to me. I'd prefer if the behaviour
of a standard mapreduce job was preserved.  

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