[jira] [Commented] (HIVE-22850) Optimise lock acquisition in TxnHandler

["Rajesh Balamohan (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-22850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17032185#comment-17032185 ] 

Rajesh Balamohan commented on HIVE-22850:
-----------------------------------------

Lock interaction matrix: https://issues.apache.org/jira/secure/attachment/12614488/HiveTransactionManagerDetailedDesign%20%281%29.pdf (Page 8)

> 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.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)