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https://issues.apache.org/jira/browse/HIVE-21354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17079388#comment-17079388
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Peter Vary commented on HIVE-21354:
-----------------------------------
I have found this in Hive 3.1:
{code:java}
EXPLAIN LOCKS SELECT * FROM web_logs;
LOCK INFORMATION:
default.web_logs -> SHARED_READ
default.web_logs.date=2015-11-18 -> SHARED_READ
default.web_logs.date=2015-11-19 -> SHARED_READ
default.web_logs.date=2015-11-20 -> SHARED_READ
default.web_logs.date=2015-11-21 -> SHARED_READ
{code}
[~gopalv], [~belugabehr]: Are you aware of any change in 4.0 which changes
this, but not backported to 3.1?
Thanks,
Peter
> 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
> 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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