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https://issues.apache.org/jira/browse/HIVE-21354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17080512#comment-17080512
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David Mollitor commented on HIVE-21354:
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[~pvary] Since the queries are always taking the table lock... why do they also 
take the partition locks?

> Lock The Entire Table If Majority Of Partitions Are Locked
> ----------------------------------------------------------
>
>                 Key: HIVE-21354
>                 URL: https://issues.apache.org/jira/browse/HIVE-21354
>             Project: Hive
>          Issue Type: Improvement
>          Components: HiveServer2
>    Affects Versions: 4.0.0, 3.2.0
>            Reporter: David Mollitor
>            Assignee: David Mollitor
>            Priority: Major
>
> One of the bottlenecks of any Hive query is the ZooKeeper locking mechanism.  
> When a Hive query interacts with a table which has a lot of partitions, this 
> may put a lot of stress on the ZK system.
> Please add a heuristic that works like this:
> # Count the number of partitions that a query is required to lock
> # Obtain the total number of partitions in the table
> # If the number of partitions accessed by the query is greater than or equal 
> to half the total number of partitions, simply create one ZNode lock at the 
> table level.
> This would improve performance of many queries, but in particular, a {{select 
> count(1) from table}} ... or ... {{select * from table limit 5}} where the 
> table has many partitions.



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