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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4123) The RLE encoding for ORC can be improved
Date Thu, 18 Jul 2013 21:48:49 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13712916#comment-13712916
] 

Owen O'Malley commented on HIVE-4123:
-------------------------------------

Comments:
* merge Utils into SerializationUtils.
* use the zigzag encode/decode in the the SerializationUtils.read/writeVslong
* move Utils.nextLong to the test code
* Utils.getTotalBytesRequired should just use long math. (n * numBits + 7) / 8 should work
* Rename IntegerCompressionReader/Writer to RunLengthIntegerReader/WriterV2
* Create an interface IntegerReader that has:
** seek
** next
** skip
* Make RunLengthIntegerReader and RunLengthIntegerReaderV2 implement IntegerReader
* The TreeReaders should declare the fields as IntegerReader.
* Each of the startStripe should use the encoding to create the right implementation of IntegerReader.
* We should do the same with an IntegerWriter interface.
* Replace fixedBitSizes with static methods in SerializationUtils:
** static int encodeBitWidth(int n)
** static int decodeBitWidth(int n)
* Finding the percentiles seems expensive, we should look at an alternative
* Why is the delta blob zigzag encoded? The sign should always be positive or negative for
the entire run.
* Maybe we could create an enum in the Writer that is the version to write that would look
like enum OrcVersion { V0_11, V0_12 } and the StreamFactory could provide the version to the
TreeWriters.


                
> The RLE encoding for ORC can be improved
> ----------------------------------------
>
>                 Key: HIVE-4123
>                 URL: https://issues.apache.org/jira/browse/HIVE-4123
>             Project: Hive
>          Issue Type: New Feature
>          Components: File Formats
>            Reporter: Owen O'Malley
>            Assignee: Prasanth J
>         Attachments: HIVE-4123.1.git.patch.txt, HIVE-4123.2.git.patch.txt, ORC-Compression-Ratio-Comparison.xlsx
>
>
> The run length encoding of integers can be improved:
> * tighter bit packing
> * allow delta encoding
> * allow longer runs

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