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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-9660) store end offset of compressed data for RG in RowIndex in ORC
Date Thu, 12 Feb 2015 02:23:11 GMT

    [ https://issues.apache.org/jira/browse/HIVE-9660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14317446#comment-14317446
] 

Sergey Shelukhin commented on HIVE-9660:
----------------------------------------

[~owen.omalley] [~alangates] [~prasanth_j] fyi... I might do it later.

I noticed that on some realistic data Prasanth was using, to read one RG out of 100, ~50%
of the data with multiple CBs was read and uncompressed.

> store end offset of compressed data for RG in RowIndex in ORC
> -------------------------------------------------------------
>
>                 Key: HIVE-9660
>                 URL: https://issues.apache.org/jira/browse/HIVE-9660
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Sergey Shelukhin
>
> Right now the end offset is estimated, which in some cases results in tons of extra data
being read.
> We can add a separate array to RowIndex (positions_v2?) that stores number of compressed
buffers for each RG, or end offset, or something, to remove this estimation magic



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