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https://issues.apache.org/jira/browse/HIVE-11786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14941867#comment-14941867
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Szehon Ho commented on HIVE-11786:
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Chatted with Chaoyu offline, this change actually looks good to me, +1.
It is a big change, but Chaoyu gave a good explanation of performance impact of
the join, and there stands to be more gain for cases like changing the
part/table names. And there seems to be good coverage via the qtests.
> 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
> 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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