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https://issues.apache.org/jira/browse/HIVE-20873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16680050#comment-16680050
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slim bouguerra commented on HIVE-20873:
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Still unclear to me why are we using Murmur, there is a dozen of other hash
algorithms including XXhash that way faster and has good quality.
https://cyan4973.github.io/xxHash/
Anyway i will try to take a look at benchmarking this i have created a sub
task. FYI XXHash is widely used by lot of MPP style engines.
> 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
> Labels: pull-request-available
> Attachments: HIVE-20873.1.patch, HIVE-20873.2.patch,
> HIVE-20873.3.patch
>
>
> 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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