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From "Josh Wills (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-132) Add configurable behavior for when a pipeline output directory already exists
Date Mon, 11 Feb 2013 03:53:13 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575611#comment-13575611
] 

Josh Wills commented on CRUNCH-132:
-----------------------------------

Definitely +1 for WriteMode.

Regarding making the naiive:

pipeline.write(pcollect1, target); 
pipeline.write(pcollect2, target); 
pipeline.run();

throw an exception, I think that the easiest way to do that would be to have MRPipeline check
to see if an equal Target is written to more than once w/o a WriteMode.APPEND being specified.
I think I can make it work, I'll cook up something this evening and post it tomorrow.
                
> Add configurable behavior for when a pipeline output directory already exists
> -----------------------------------------------------------------------------
>
>                 Key: CRUNCH-132
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-132
>             Project: Crunch
>          Issue Type: Improvement
>    Affects Versions: 0.4.0
>            Reporter: Dave Beech
>            Assignee: Josh Wills
>         Attachments: CRUNCH-132.patch, CRUNCH-132-proto.patch
>
>
> 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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