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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-19416) Create single version transactional table metastore statistics for aggregation queries
Date Tue, 12 Jun 2018 22:15:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-19416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16510309#comment-16510309
] 

Sergey Shelukhin commented on HIVE-19416:
-----------------------------------------

Another concern is that the code that gets the snapshot looks like it may affect locks/etc
(LockException was added) or get write Ids outside where they are normally retrieved (in stats
optimizer). 
I think optimizer runs before the locks are obtained, so this can lead to deadlocks if locks
are obtained piecemeal, and also to some consistency issues I assume. It's not clear what
to do to get correct/incorrect stats info for it, without the locks. Maybe locks would have
to be moved before the optimizer. cc [~ekoifman] 

> Create single version transactional table metastore statistics for aggregation queries
> --------------------------------------------------------------------------------------
>
>                 Key: HIVE-19416
>                 URL: https://issues.apache.org/jira/browse/HIVE-19416
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>            Reporter: Steve Yeom
>            Assignee: Steve Yeom
>            Priority: Major
>
> The system should use only statistics for aggregation queries like count on transactional
tables.



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