[jira] [Comment Edited] (HIVE-21354) Lock The Entire Table If Majority Of Partitions Are Locked

["David Mollitor (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-21354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17080512#comment-17080512 ] 

David Mollitor edited comment on HIVE-21354 at 4/10/20, 3:43 PM:
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[~pvary] Since the queries are always taking the table lock... why do they also bother to take the partition locks?


was (Author: belugabehr):
[~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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