hive-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Kevin Wilfong (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-4005) Column truncation
Date Sat, 09 Feb 2013 06:49:14 GMT

     [ https://issues.apache.org/jira/browse/HIVE-4005?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kevin Wilfong updated HIVE-4005:
--------------------------------

    Status: Patch Available  (was: Open)
    
> Column truncation
> -----------------
>
>                 Key: HIVE-4005
>                 URL: https://issues.apache.org/jira/browse/HIVE-4005
>             Project: Hive
>          Issue Type: New Feature
>          Components: CLI
>    Affects Versions: 0.11.0
>            Reporter: Kevin Wilfong
>            Assignee: Kevin Wilfong
>         Attachments: HIVE-4005.1.patch.txt, HIVE-4005.2.patch.txt
>
>
> Column truncation allows users to remove data for columns that are no longer useful.
> This is done by removing the data for the column and setting the length of the column
data and related lengths to 0 in the RC file header.
> RC file was fixed to recognize columns with lengths of zero to be empty and are treated
as if the column doesn't exist in the data, a null is returned for every value of that column
in every row. This is the same thing that happens when more columns are selected than exist
in the file.
> A new command was added to the CLI
> TRUNCATE TABLE ... PARTITION ... COLUMNS ...
> This launches a map only job where each mapper rewrites a single file without the unnecessary
column data and the adjusted headers. It does not uncompress/deserialize the data so it is
much faster than rewriting the data with NULLs.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message