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Posted to dev@hive.apache.org by "Prasanth Jayachandran (JIRA)" <ji...@apache.org> on 2015/02/07 02:06:34 UTC
[jira] [Updated] (HIVE-9392) JoinStatsRule miscalculates join
cardinality as incorrect NDV is used due to column names having duplicated
fqColumnName
[ https://issues.apache.org/jira/browse/HIVE-9392?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Prasanth Jayachandran updated HIVE-9392:
----------------------------------------
Fix Version/s: (was: 0.15.0)
> 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.
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