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From "Jie Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PIG-483) PERFORMANCE: different strategies for large and small order bys
Date Wed, 27 Jun 2012 23:26:44 GMT

    [ https://issues.apache.org/jira/browse/PIG-483?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13402661#comment-13402661

Jie Li commented on PIG-483:

For the skew join, if the partition table turns out to be small, then we can convert it to
a normal join, which doesn't need the sampler either. Would open another jira for that.
> PERFORMANCE: different strategies for large and small order bys
> ---------------------------------------------------------------
>                 Key: PIG-483
>                 URL: https://issues.apache.org/jira/browse/PIG-483
>             Project: Pig
>          Issue Type: Improvement
>    Affects Versions: 0.2.0
>            Reporter: Olga Natkovich
>              Labels: gsoc2011, performance
> Currently pig always does a multi-pass order by where it first determines a distribution
for the keys and then orders in a second pass.  This avoids the necessity of having a single
reducer.  However, in cases where the data is small enough to fit into a single reducer, this
is inefficient.  For small data sets it would be good to realize the small size of the set
and do the order by in a single pass with a single reducer.
> This is a candidate project for Google summer of code 2011. More information about the
program can be found at http://wiki.apache.org/pig/GSoc2011

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