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From "Doug Cutting (JIRA)" <>
Subject [jira] [Commented] (HIVE-3874) Create a new Optimized Row Columnar file format for Hive
Date Thu, 10 Jan 2013 18:26:13 GMT


Doug Cutting commented on HIVE-3874:

Owen, did you consider proposing improvements to Trevni instead?

Addressing your four points of distinction with Trevni:

 - How is Trevni's type model incompatible with Hive?  Is the irreparable?
 - Might dictionaries be somehow added to Trevni?
 - What sort of indexes are required in addition to those that Trevni supports, where the
initial value of every block may be stored before all the blocks, permitting random access
by value to the blocks?  If something different is required, might that be added to Trevni?
 - Trevni uses relatively small compression blocks (~64k) that may be skipped.  How would
block mode substantially improve this?  If it would, might this change be made to Trevni?

> Create a new Optimized Row Columnar file format for Hive
> --------------------------------------------------------
>                 Key: HIVE-3874
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Serializers/Deserializers
>            Reporter: Owen O'Malley
>            Assignee: Owen O'Malley
>         Attachments: OrcFileIntro.pptx
> 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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