[
https://issues.apache.org/jira/browse/HIVE-20873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16677097#comment-16677097
]
ASF GitHub Bot commented on HIVE-20873:
---------------------------------------
GitHub user pudidic opened a pull request:
https://github.com/apache/hive/pull/485
HIVE-20873: Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce…
… hash collision (Teddy Choi)
Change-Id: Ie3ae307acb331c48bc5e1cb9c417cd5d1d792f50
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/pudidic/hive HIVE-20873
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/hive/pull/485.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #485
----
commit b658957051c9f75861cd75383f5239a76dfb9f0e
Author: Teddy Choi <tchoi@...>
Date: 2018-11-06T18:02:26Z
HIVE-20873: Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce hash
collision (Teddy Choi)
Change-Id: Ie3ae307acb331c48bc5e1cb9c417cd5d1d792f50
----
> 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
>
>
> 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.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
