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Posted to dev@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2014/05/23 23:37:02 UTC

[jira] [Updated] (HIVE-7121) Use murmur hash to distribute HiveKey

     [ https://issues.apache.org/jira/browse/HIVE-7121?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gopal V updated HIVE-7121:
--------------------------

    Attachment: HIVE-7121.WIP.patch

> Use murmur hash to distribute HiveKey
> -------------------------------------
>
>                 Key: HIVE-7121
>                 URL: https://issues.apache.org/jira/browse/HIVE-7121
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Gopal V
>            Assignee: Gopal V
>         Attachments: HIVE-7121.WIP.patch
>
>
> The current hashCode implementation produces poor parallelism when dealing with single integers or doubles.
> And for partitioned inserts into a 1 bucket table, there is a significant hotspot on Reducer #31.
> Removing the magic number 31 and using a more normal hash algorithm would help fix these hotspots.



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