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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (HIVE-7428) OrcSplit fails to account for columnar projections in its size estimates
Date Thu, 30 Apr 2015 13:46:06 GMT

     [ https://issues.apache.org/jira/browse/HIVE-7428?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gopal V reassigned HIVE-7428:
-----------------------------

    Assignee: Gopal V  (was: Prasanth Jayachandran)

> OrcSplit fails to account for columnar projections in its size estimates
> ------------------------------------------------------------------------
>
>                 Key: HIVE-7428
>                 URL: https://issues.apache.org/jira/browse/HIVE-7428
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Gopal V
>            Assignee: Gopal V
>
> Currently, ORC generates splits based on stripe offset + stripe length.
> This means that the splits for all columnar projections are exactly the same size, despite
reading the footer which gives the estimated sizes for each column.
> This is a hold-out from FileSplit which uses getLen() as the I/O cost of reading a file
in a map-task.
> RCFile didn't have a footer with column statistics information, but for ORC this would
be extremely useful to reduce task overheads when processing extremely wide tables with highly
selective column projections.



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