[jira] Commented: (HIVE-1841) datanucleus.fixedDatastore should be true in hive-default.xml

["Ning Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-1841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12969413#action_12969413 ] 

Ning Zhang commented on HIVE-1841:
----------------------------------

The hive-default.xml only set the first to true. This is good for first-time users to quickly get things started (by automatically creating tables needed by metastore) without changing any configurations. This removes frictions for the beginners. 

For experts or administrators for production clusters, these parameters can be set in hive-site.xml. This is actually what we are doing at Facebook (setting fixed metastore schema). I think this will give you both the flexibility/configurability as well as security. What do you think?

>  datanucleus.fixedDatastore should be true in hive-default.xml
> --------------------------------------------------------------
>
>                 Key: HIVE-1841
>                 URL: https://issues.apache.org/jira/browse/HIVE-1841
>             Project: Hive
>          Issue Type: Improvement
>          Components: Configuration
>    Affects Versions: 0.6.0
>            Reporter: Edward Capriolo
>             Fix For: 0.7.0
>
>
> Two datanucleus variables:
> {noformat}
> <property>
>  <name>datanucleus.autoCreateSchema</name>
>  <value>false</value>
> </property>
> <property>
>  <name>datanucleus.fixedDatastore</name>
>  <value>true</value>
> </property>
> {noformat}
> are dangerous.  We do want the schema to auto-create itself, but we do not want the schema to auto update itself. 
> Someone might accidentally point a trunk at the wrong meta-store and unknowingly update. I believe we should set this to false and possibly trap exceptions stemming from hive wanting to do any update. This way someone has to actively acknowledge the update, by setting this to true and then starting up hive, or leaving it false, removing schema modifies for the user that hive usages, and doing all the time and doing the updates by hand. 

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