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From "Aihua Xu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11402) HS2 - disallow parallel query execution within a single Session
Date Tue, 05 Jul 2016 18:56:11 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15363011#comment-15363011
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Aihua Xu commented on HIVE-11402:
---------------------------------

hmm. Yeah. Saw your comments in HiveSessionImpl and we do have issues  that some variables
in SessionState are not protected for multiple threads.

Seems to make sense to have such option and continue fixing the thread-safe issue. Just wondering
if the option is set to false, what kind of effect to the new operation in the same session?
will it just get blocked to get the previous one finished?  



> HS2 - disallow parallel query execution within a single Session
> ---------------------------------------------------------------
>
>                 Key: HIVE-11402
>                 URL: https://issues.apache.org/jira/browse/HIVE-11402
>             Project: Hive
>          Issue Type: Bug
>          Components: HiveServer2
>            Reporter: Thejas M Nair
>            Assignee: Sergey Shelukhin
>         Attachments: HIVE-11402.01.patch, HIVE-11402.02.patch, HIVE-11402.patch
>
>
> HiveServer2 currently allows concurrent queries to be run in a single session. However,
every HS2 session has  an associated SessionState object, and the use of SessionState in many
places assumes that only one thread is using it, ie it is not thread safe.
> There are many places where SesssionState thread safety needs to be addressed, and until
then we should serialize all query execution for a single HS2 session. -This problem can become
more visible with HIVE-4239 now allowing parallel query compilation.-
> Note that running queries in parallel for single session is not straightforward  with
jdbc, you need to spawn another thread as the Statement.execute calls are blocking. I believe
ODBC has non blocking query execution API, and Hue is another well known application that
shares sessions for all queries that a user runs.



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