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From "Josh Wills (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CRUNCH-23) PCollection#sort doesn't do a full sort on values
Date Fri, 03 Aug 2012 15:29:03 GMT

    [ https://issues.apache.org/jira/browse/CRUNCH-23?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13428185#comment-13428185
] 

Josh Wills commented on CRUNCH-23:
----------------------------------

Thanks man, I'll take a look at it this weekend. I think the reservoir sampling approach should
work-- either a) the data isn't very large, and so the quality of the sample won't matter
that much, or b) the data is large and the sample will be good w/high probability.
                
> PCollection#sort doesn't do a full sort on values
> -------------------------------------------------
>
>                 Key: CRUNCH-23
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-23
>             Project: Crunch
>          Issue Type: Bug
>            Reporter: Gabriel Reid
>            Assignee: Rahul Sharma
>         Attachments: 0001-CRUNCH-23-fix-sorting.patch, CRUNCH-23-used-TotalOrderpartioner-for-sorting-keys.patch,
SortTest.java
>
>
> When a PCollection is sorted (using PCollection#sort), the sorting that is performed
is only per reducer, and not an absolute sort over all values. This means that the values
are not in sorted order if they are iterated over on a materialized collection. It also means
that the sorted files that are output from a sort operation can not be simply concatenated
to come to a single sorted file.

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