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https://issues.apache.org/jira/browse/HIVE-9741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14335584#comment-14335584
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Xiaobing Zhou commented on HIVE-9741:
-------------------------------------
Thanks [~sershe] for review. If setDbANSIMode() call is moved to somewhere like
patch V4. DB query within critical section still can not be avoided as the
stack trace shows. This is a problem, do you have any comments?
MetaStoreDirectSql.determineDbType(...)
MetaStoreDirectSql.MetaStoreDirectSql(...)
ObjectStore.initialize(...)
ObjectStore.setConf(…)
DB type detections is actually manually tested agains different backend, works
well.
> 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
>
>
> 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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