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Posted to dev@hive.apache.org by "Xuefu Zhang (JIRA)" <ji...@apache.org> on 2014/12/24 00:53:13 UTC

[jira] [Commented] (HIVE-9199) Excessive exclusive lock used in some DDLs with DummyTxnManager

    [ 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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