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https://issues.apache.org/jira/browse/PIG-483?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13403635#comment-13403635
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Jie Li commented on PIG-483:
----------------------------
Ooops, forgot that the sample job will always use 1 reducer instead of the
estimated #reducer, so we don't have the information to decide whether to skip
it.
One option is to add a field in MapReduceOper to store the estimated #reducer?
> 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
> Attachments: PIG-483.0.patch
>
>
> 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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