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From "Chaoyu Tang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11786) Deprecate the use of redundant column in colunm stats related tables
Date Wed, 07 Oct 2015 22:58:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14947760#comment-14947760
] 

Chaoyu Tang commented on HIVE-11786:
------------------------------------

Thanks [~sseth]. Maybe there are a large number of rows in TAB_COL_STATS/PART_COL_STATS, so
it took a long time to create the index on their column "COLUMN_NAME". I am going to change
the query to see if it is helpful. BTW, I have created a JIRA HIVE-12053 for the performance
regression you found.

> 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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