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Posted to issues@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2015/04/30 15:46:06 UTC
[jira] [Assigned] (HIVE-7428) OrcSplit fails to account for
columnar projections in its size estimates
[ 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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