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Date: Wed, 7 Oct 2015 23:38:26 +0000 (UTC)
From: "Siddharth Seth (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
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Subject: [jira] [Commented] (HIVE-11786) Deprecate the use of redundant
 column in colunm stats related tables
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    [ https://issues.apache.org/jira/browse/HIVE-11786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14947807#comment-14947807 ] 

Siddharth Seth commented on HIVE-11786:
---------------------------------------

Yes.  There's a large number of entries - 2million+ in PART_COL_STATS. The number of new entries there is what I was worried about - how many new entries per table / partition, and whether that can have a significant impact. IAC, if the query is being re-written - maybe the indexes will not be required.

> Deprecate the use of redundant column in colunm stats related tables
> --------------------------------------------------------------------
>
>                 Key: HIVE-11786
>                 URL: https://issues.apache.org/jira/browse/HIVE-11786
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>            Reporter: Chaoyu Tang
>            Assignee: Chaoyu Tang
>             Fix For: 1.3.0, 2.0.0
>
>         Attachments: HIVE-11786.1.patch, HIVE-11786.1.patch, HIVE-11786.2.patch, HIVE-11786.patch
>
>
> The stats tables such as TAB_COL_STATS, PART_COL_STATS have redundant columns such as DB_NAME, TABLE_NAME, PARTITION_NAME since these tables already have foreign key like TBL_ID, or PART_ID referencing to TBLS or PARTITIONS. 
> These redundant columns violate database normalization rules and cause a lot of inconvenience (sometimes difficult) in column stats related feature implementation. For example, when renaming a table, we have to update TABLE_NAME column in these tables as well which is unnecessary.
> This JIRA is first to deprecate the use of these columns at HMS code level. A followed JIRA is to be opened to focus on DB schema change and upgrade.


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