[
https://issues.apache.org/jira/browse/HIVE-9392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14521792#comment-14521792
]
Pengcheng Xiong commented on HIVE-9392:
---------------------------------------
[~prasanth_j] and [~mohammedmostafa], could u plz let [~jpullokkaran] and I
know if it is resolved already or it needs further efforts? thanks.
> JoinStatsRule miscalculates join cardinality as incorrect NDV is used due to
> column names having duplicated fqColumnName
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: HIVE-9392
> URL: https://issues.apache.org/jira/browse/HIVE-9392
> Project: Hive
> Issue Type: Bug
> Components: Physical Optimizer
> Affects Versions: 0.14.0
> Reporter: Mostafa Mokhtar
> Assignee: Prasanth Jayachandran
> Priority: Critical
> Attachments: HIVE-9392.1.patch, HIVE-9392.2.patch
>
>
> In JoinStatsRule.process the join column statistics are stored in HashMap
> joinedColStats, the key used which is the ColStatistics.fqColName is
> duplicated between join column in the same vertex, as a result distinctVals
> ends up having duplicated values which negatively affects the join
> cardinality estimation.
> The duplicate keys are usually named KEY.reducesinkkey0.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
