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From "Tim Armstrong" <tim.g.armstr...@gmail.com>
Subject Re: Review Request: Optimisation for RCFile reading to improve CPU usage.
Date Thu, 11 Aug 2011 23:07:05 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/1309/
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(Updated 2011-08-11 23:07:05.774106)


Review request for hive, Yongqiang He and Ning Zhang.


Changes
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Minor change to avoid a compilation problem.


Summary
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By tweaking the RCFile$Reader implementation to allow more efficient memory access I was able
to reduce CPU usage. I measured the speed required to scan a gzipped RCFile, decompress and
assemble into records. CPU time was reduced by about 7% for a full table scan, An improvement
of about 2% was realised when a smaller subset of columns (3-5 out of tens) were selected.


This addresses bug HIVE-2350.
    https://issues.apache.org/jira/browse/HIVE-2350


Diffs (updated)
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  trunk/ql/src/java/org/apache/hadoop/hive/ql/io/RCFile.java 1156839 

Diff: https://reviews.apache.org/r/1309/diff


Testing
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Ran TestRCFile unit test.  Manually tested reading from warehouse table.


Thanks,

Tim


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