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From "Kevin Wilfong (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3874) Create a new Optimized Row Columnar file format for Hive
Date Tue, 05 Feb 2013 02:39:11 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13570888#comment-13570888
] 

Kevin Wilfong commented on HIVE-3874:
-------------------------------------

@Owen: Here's a couple more issues I ran into, and again I can file JIRAs for these later
once the code is checked in.

Incorrect deserialization of doubles (leads to a lot of NaNs)
https://reviews.facebook.net/D8379

Strings are written incorrectly when they span two chunks of a DynamicByteArray
E.g. say the original string is 'abcdefghi' the string written in the ORC file may be 'abcdefabc'
https://reviews.facebook.net/D8385
                
> Create a new Optimized Row Columnar file format for Hive
> --------------------------------------------------------
>
>                 Key: HIVE-3874
>                 URL: https://issues.apache.org/jira/browse/HIVE-3874
>             Project: Hive
>          Issue Type: Improvement
>          Components: Serializers/Deserializers
>            Reporter: Owen O'Malley
>            Assignee: Owen O'Malley
>         Attachments: hive.3874.2.patch, OrcFileIntro.pptx, orc.tgz
>
>
> There are several limitations of the current RC File format that I'd like to address
by creating a new format:
> * each column value is stored as a binary blob, which means:
> ** the entire column value must be read, decompressed, and deserialized
> ** the file format can't use smarter type-specific compression
> ** push down filters can't be evaluated
> * the start of each row group needs to be found by scanning
> * user metadata can only be added to the file when the file is created
> * the file doesn't store the number of rows per a file or row group
> * there is no mechanism for seeking to a particular row number, which is required for
external indexes.
> * there is no mechanism for storing light weight indexes within the file to enable push-down
filters to skip entire row groups.
> * the type of the rows aren't stored in the file

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