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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2350) Improve RCFile Read Speed
Date Fri, 05 Aug 2011 16:37:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13080059#comment-13080059
] 

Ning Zhang commented on HIVE-2350:
----------------------------------

Also is this patch read for review? If so you can set the JIRA's status to "Patch Available".

> 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
>         Attachments: rcfile-2011-08-04.diff
>
>   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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