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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-9199) Excessive exclusive lock used in some DDLs with DummyTxnManager
Date Tue, 23 Dec 2014 23:53:13 GMT

    [ https://issues.apache.org/jira/browse/HIVE-9199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14257696#comment-14257696
] 

Xuefu Zhang commented on HIVE-9199:
-----------------------------------

With my limited understanding, the patch looks okay. To be sure, [~alangates], would you mind
taking a look also?

> Excessive exclusive lock used in some DDLs with DummyTxnManager
> ---------------------------------------------------------------
>
>                 Key: HIVE-9199
>                 URL: https://issues.apache.org/jira/browse/HIVE-9199
>             Project: Hive
>          Issue Type: Bug
>          Components: Locking
>            Reporter: Chaoyu Tang
>            Assignee: Chaoyu Tang
>         Attachments: HIVE-9199.patch
>
>
> In DummyTxnManager, the lockMode for a WriteEntity (e.g. database, table) is determined
by "complete" instead of its writeType. But since DDL output WriteEntity is usually complete,
some DDL operations might be given exclusive locks which are actually not needed, which causes
unnecessary locking contention. For example, in createTable, DummyTxnManager suggests an exclusive
lock to table database writeentity since it is complete.



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