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From "Rahul Sharma (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CRUNCH-23) PCollection#sort doesn't do a full sort on values
Date Fri, 03 Aug 2012 07:35:02 GMT

     [ https://issues.apache.org/jira/browse/CRUNCH-23?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rahul Sharma updated CRUNCH-23:
-------------------------------

    Attachment: 0001-CRUNCH-23-fix-sorting.patch

Josh, I have implemented the same solution. But I feel that the data distribution is not perfect
there. 

The solution is based on reservoir sampling. So the keys that are used in the Partioner are
selected from a subset of the data. It solely depends on how good is the subset sample.  
                
> 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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