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Posted to dev@pig.apache.org by "Jie Li (JIRA)" <ji...@apache.org> on 2012/06/28 04:30:44 UTC
[jira] [Updated] (PIG-483) PERFORMANCE: different strategies for
large and small order bys
[ https://issues.apache.org/jira/browse/PIG-483?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jie Li updated PIG-483:
-----------------------
Attachment: PIG-483.0.patch
Attached a patch that introduced SkipJob. The output of order-by on small dataset would look like:
Job Stats (time in seconds):
JobId Alias Feature Outputs
job_local_0001 a MAP_ONLY
job_local_0002 b ORDER_BY file:/tmp/temp-107984693/tmp2050404975,
skipped_job b SAMPLER
Input(s):
Successfully read records from: "file:///Users/JieLi/git/pig-git/1.txt"
Output(s):
Successfully stored records in: "file:/tmp/temp-107984693/tmp2050404975"
Job DAG:
job_local_0001 -> skipped_job,
skipped_job -> job_local_0002,
job_local_0002
> 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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