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From "ASF GitHub Bot (Jira)" <>
Subject [jira] [Work logged] (HIVE-20873) Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce hash collision
Date Tue, 16 Jun 2020 16:54:02 GMT


ASF GitHub Bot logged work on HIVE-20873:

                Author: ASF GitHub Bot
            Created on: 16/Jun/20 16:53
            Start Date: 16/Jun/20 16:53
    Worklog Time Spent: 10m 
      Work Description: github-actions[bot] closed pull request #485:


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Issue Time Tracking

    Worklog Id:     (was: 446670)
    Time Spent: 20m  (was: 10m)

> Use Murmur hash for VectorHashKeyWrapperTwoLong to reduce hash collision
> ------------------------------------------------------------------------
>                 Key: HIVE-20873
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Teddy Choi
>            Assignee: Teddy Choi
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0
>         Attachments: HIVE-20873.1.patch, HIVE-20873.2.patch, HIVE-20873.3.patch
>          Time Spent: 20m
>  Remaining Estimate: 0h
> 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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