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https://issues.apache.org/jira/browse/HIVE-7428?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gopal V updated HIVE-7428:
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Attachment: HIVE-7428.2.patch
> 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
> Affects Versions: 1.2.0, 1.3.0
> Reporter: Gopal V
> Assignee: Gopal V
> Attachments: HIVE-7428.1.patch, HIVE-7428.2.patch
>
>
> 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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