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From "Chaoyu Tang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-9199) Excessive exclusive lock used in some DDLs with DummyTxnManager
Date Tue, 23 Dec 2014 19:17:13 GMT

     [ https://issues.apache.org/jira/browse/HIVE-9199?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chaoyu Tang updated HIVE-9199:
------------------------------
    Attachment: HIVE-9199.patch

The attached patch is to change DummayTxnManager to determine the lockMode for DDL based on
output writetype, while still using "complete" for DML operations. 
Please help review on RB https://reviews.apache.org/r/29374/ , thanks in advance.

> 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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