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