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Posted to issues@hive.apache.org by "Teddy Choi (JIRA)" <ji...@apache.org> on 2018/11/06 18:00:04 UTC

[jira] [Assigned] (HIVE-20873) Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce hash collision

     [ https://issues.apache.org/jira/browse/HIVE-20873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Teddy Choi reassigned HIVE-20873:
---------------------------------


> Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce hash collision
> ------------------------------------------------------------------------
>
>                 Key: HIVE-20873
>                 URL: https://issues.apache.org/jira/browse/HIVE-20873
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Teddy Choi
>            Assignee: Teddy Choi
>            Priority: Major
>
> VectorHashKeyWrapperTwoLong is implemented with few bit shift operators and XOR operators for short computation time, but more hash collision. Group by operations become very slow on large data sets. It needs Murmur hash or a better hash function for less hash collision.



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