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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-9741) Refactor MetaStoreDirectSql constructor by removing DB queries out of critical section
Date Wed, 25 Feb 2015 22:03:05 GMT

    [ https://issues.apache.org/jira/browse/HIVE-9741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14337307#comment-14337307
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Sergey Shelukhin commented on HIVE-9741:
----------------------------------------

Hi. What I'm asking is - why is setDbANSIMode necessary during init with these changes? And
logging is no longer valid at all since this method is no longer used for verification.



> Refactor MetaStoreDirectSql constructor by removing DB queries out of critical section
> --------------------------------------------------------------------------------------
>
>                 Key: HIVE-9741
>                 URL: https://issues.apache.org/jira/browse/HIVE-9741
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>    Affects Versions: 1.0.0
>            Reporter: Xiaobing Zhou
>            Assignee: Xiaobing Zhou
>         Attachments: HIVE-9741.1.patch, HIVE-9741.2.patch, HIVE-9741.3.patch, HIVE-9741.4.patch,
HIVE-9741.5.patch
>
>
> MetaStoreDirectSql constructor is querying DB to determine dbType, which leads to too
many DB queries to make megastore slow as ObjectStore.setConf might be called frequently.
Moreover, ObjectStore.setConf begins/ends with lock acquire/release, if the underlying DB
hangs somehow, lock is never released and all hereafter incoming requests are blocked.
> Two points:
> 1. Using getProductName based JDBC driver to get dbType info.
> 2. Since metastore auto-creaton is disabled by default, it'd better bypass ensureDbInit()
and runTestQuery() in order to avoid DB queries within critical section of setConf.
> Here’s stack trace:
> MetaStoreDirectSql.determineDbType(...)
> MetaStoreDirectSql.MetaStoreDirectSql(...)
> ObjectStore.initialize(...)
> ObjectStore.setConf(…)



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