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Date: Thu, 18 Aug 2011 22:26:27 +0000 (UTC)
From: "Tim Armstrong (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
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Subject: [jira] [Commented] (HIVE-2350) Improve RCFile Read Speed
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    [ https://issues.apache.org/jira/browse/HIVE-2350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13087352#comment-13087352 ] 

Tim Armstrong commented on HIVE-2350:
-------------------------------------

Hi Carl, 
  Was this committed to trunk?  I'm not seeing it there

> Improve RCFile Read Speed
> -------------------------
>
>                 Key: HIVE-2350
>                 URL: https://issues.apache.org/jira/browse/HIVE-2350
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Tim Armstrong
>            Assignee: Tim Armstrong
>            Priority: Minor
>             Fix For: 0.8.0
>
>         Attachments: rcfile-2011-08-04.diff, rcfile_opt_2011-08-05.diff, rcfile_opt_2011-08-05b.diff, rcfile_opt_2011-08-11.patch
>
>   Original Estimate: 0h
>  Remaining Estimate: 0h
>
> 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.

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