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From "Rajesh Balamohan (Jira)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-22850) Optimise lock acquisition in TxnHandler
Date Fri, 07 Feb 2020 08:05:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-22850?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rajesh Balamohan updated HIVE-22850:
------------------------------------
    Attachment: Screenshot 2020-02-07 at 4.14.51 AM.png

> Optimise lock acquisition in TxnHandler
> ---------------------------------------
>
>                 Key: HIVE-22850
>                 URL: https://issues.apache.org/jira/browse/HIVE-22850
>             Project: Hive
>          Issue Type: Improvement
>          Components: Hive
>            Reporter: Rajesh Balamohan
>            Priority: Major
>         Attachments: HIVE-22850.1.patch, Screenshot 2020-02-07 at 4.14.51 AM.png
>
>
> With concurrent queries, time taken for lock acquisition increases substantially. As
part of lock acquisition in the query, {{TxnHandler::checkLock}} gets invoked. This involves
getting a mutex and compare the locks being requested for, with that of existing locks in
{{HIVE_LOCKS}} table.
> With concurrent queries, time taken to do this check increase and this significantly
increases the time taken for getting mutex for other threads (due to select for update). In
a synthetic workload, it was in the order of 10+ seconds. This codepath can be optimized when
all lock requests are SHARED_READ.



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