[jira] [Resolved] (HIVE-24575) VectorGroupByOperator reusing keys can lead to wrong results

["Mustafa İman (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-24575?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mustafa İman resolved HIVE-24575.
---------------------------------
    Resolution: Fixed

> VectorGroupByOperator reusing keys can lead to wrong results
> ------------------------------------------------------------
>
>                 Key: HIVE-24575
>                 URL: https://issues.apache.org/jira/browse/HIVE-24575
>             Project: Hive
>          Issue Type: Bug
>          Components: Vectorization
>            Reporter: Zhihua Deng
>            Assignee: Zhihua Deng
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 4.0.0
>
>          Time Spent: 40m
>  Remaining Estimate: 0h
>
>  A common sql like
> {code:java}
> select category as category, count(distinct maskdid) as uv from dwd_internal_inc_d group by category{code}
> can have a wrong result on the trunk,  the result of column category can be confused and
> aggregate of distinct maskdid is also wrong. 
> After some debugging, We find that the problem is caused by wrong byteStarts[i] when using it to copy the current keys to the reusable keys: 
> [https://github.com/apache/hive/blob/master/ql/src/java/org/apache/hadoop/hive/ql/exec/vector/wrapper/VectorHashKeyWrapperGeneral.java#L351-L362]
> The byteStarts[i] is always 0 due to Arrays.fill(byteStarts, 0); so it copies the range from 0 other then the real start index to len of the current keys to the reusable keys when clone.byteValues[i].length >= byteValues[i].length met, which results to the problem.
>  
>  



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