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From "Shreepadma Venugopalan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3764) Support metastore version consistency check
Date Mon, 03 Dec 2012 23:04:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3764?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13509300#comment-13509300
] 

Shreepadma Venugopalan commented on HIVE-3764:
----------------------------------------------

I think adding the consistency check is a good idea too. I've not looked into all the details
of the code, but I noticed that the metastore version number is the hive release version.
While this makes the version numbers easily readable, we would need to provide scripts and
perform a metastore upgrade on every Hive release even if there are no other patches in the
release that require a metastore schema upgrade. The other option would be to use version
numbers from a monotonically increasing sequence instead and bump up the version number only
if there are changes in a release that require a metastore upgrade. Wondering if you have
considered the later option. Thanks.
                
> Support metastore version consistency check
> -------------------------------------------
>
>                 Key: HIVE-3764
>                 URL: https://issues.apache.org/jira/browse/HIVE-3764
>             Project: Hive
>          Issue Type: Improvement
>          Components: Metastore
>            Reporter: Prasad Mujumdar
>            Assignee: Prasad Mujumdar
>             Fix For: 0.10.0
>
>         Attachments: HIVE-3764-1.patch
>
>
> Today there's no version/compatibility information stored in hive metastore. Also the
datanucleus configuration property to automatically create missing tables is enabled by default.
If you happen to start an older or newer hive or don't run the correct upgrade scripts during
migration, the metastore would end up corrupted. The autoCreate schema is not always sufficient
to upgrade metastore when migrating to newer release. It's not supported with all databases.
Besides the migration often involves altering existing table, changing or moving data etc.
> Hence it's very useful to have some consistency check to make sure that hive is using
correct metastore and for production systems the schema is not automatically by running hive.

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