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Date: Wed, 25 Feb 2015 22:03:05 +0000 (UTC)
From: "Sergey Shelukhin (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
Message-ID: <JIRA.12776501.1424455519000.15335.1424901785272@Atlassian.JIRA>
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Subject: [jira] [Commented] (HIVE-9741) Refactor MetaStoreDirectSql
 constructor by removing DB queries out of critical section
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    [ https://issues.apache.org/jira/browse/HIVE-9741?page=3Dcom.atlassian.=
jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D14337=
307#comment-14337307 ]=20

Sergey Shelukhin commented on HIVE-9741:
----------------------------------------

Hi. What I'm asking is - why is setDbANSIMode necessary during init with th=
ese 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 And logging is no longer valid at all since this method is no =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 cri=
tical 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.pa=
tch, 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 rel=
eased 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 bypas=
s ensureDbInit() and runTestQuery() in order to avoid DB queries within cri=
tical section of setConf.
> Here=E2=80=99s stack trace:
> MetaStoreDirectSql.determineDbType(...)
> MetaStoreDirectSql.MetaStoreDirectSql(...)
> ObjectStore.initialize(...)
> ObjectStore.setConf(=E2=80=A6)


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