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From "Tim Armstrong" <>
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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(Updated 2011-08-11 23:07:05.774106)

Review request for hive, Yongqiang He and Ning Zhang.


Minor change to avoid a compilation problem.


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.

Diffs (updated)

  trunk/ql/src/java/org/apache/hadoop/hive/ql/io/ 1156839 



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



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