[
https://issues.apache.org/jira/browse/HIVE-7074?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Gopal V resolved HIVE-7074.
---------------------------
Resolution: Not a Problem
> The reducer parallelism should be a prime number for better stride protection
> -----------------------------------------------------------------------------
>
> Key: HIVE-7074
> URL: https://issues.apache.org/jira/browse/HIVE-7074
> Project: Hive
> Issue Type: Improvement
> Components: Statistics
> Reporter: Gopal V
> Assignee: Gopal V
> Attachments: HIVE-7074.1.patch
>
>
> The current hive reducer parallelism results in stride issues with key
> distribution.
> a JOIN generating even numbers will get strided onto only some of the
> reducers.
> The probability of distribution skew is controlled by the number of common
> factors shared by the hashcode of the key and the number of buckets.
> Using a prime number within the reducer estimation will cut that probability
> down by a significant amount.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
