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From "Prasanth J (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-7859) Tune zlib compression in ORC to account for the encoding strategy
Date Wed, 10 Sep 2014 19:11:33 GMT

    [ https://issues.apache.org/jira/browse/HIVE-7859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14128942#comment-14128942
] 

Prasanth J commented on HIVE-7859:
----------------------------------

I like the patch. LGTM +1. Pending unit test runs.

Under "COMPRESSION" strategy have you tried using zlib.BEST_COMPRESSION instead of zlib.DEFAULT_COMPRESSION
to see the changes to space vs time? 


> Tune zlib compression in ORC to account for the encoding strategy
> -----------------------------------------------------------------
>
>                 Key: HIVE-7859
>                 URL: https://issues.apache.org/jira/browse/HIVE-7859
>             Project: Hive
>          Issue Type: Bug
>          Components: File Formats
>            Reporter: Gopal V
>            Assignee: Gopal V
>         Attachments: HIVE-7859.1.patch, HIVE-7859.2.patch
>
>
> Currently ORC Zlib is slow because several compression strategies ZLib uses is already
done by ORC in itself (dictionary, RLE, bit-packing).
> We need to pick between Z_FILTERED, Z_HUFFMAN_ONLY, Z_RLE, Z_FIXED and Z_DEFAULT_STRATEGY
according to column stream type.
> For instance an RLE_V2 stream could a use Z_FILTERED compression without invoking the
rest of the strategies.
> The string streams can use Z_FIXED compression strategies and so on.
> The core limitation to stick to retain compatibility with the default decompressor, so
that these are automatically backward compatible.



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