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https://issues.apache.org/jira/browse/HIVE-23365?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stamatis Zampetakis updated HIVE-23365:
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Attachment: HIVE-23365.03.patch
> Put RS deduplication optimization under cost based decision
> -----------------------------------------------------------
>
> Key: HIVE-23365
> URL: https://issues.apache.org/jira/browse/HIVE-23365
> Project: Hive
> Issue Type: Improvement
> Components: Physical Optimizer
> Reporter: Jesus Camacho Rodriguez
> Assignee: Stamatis Zampetakis
> Priority: Major
> Attachments: HIVE-23365.01.patch, HIVE-23365.02.patch,
> HIVE-23365.03.patch
>
>
> Currently, RS deduplication is always executed whenever it is semantically
> correct. However, it could be beneficial to leave both RS operators in the
> plan, e.g., if the NDV of the second RS is very low. Thus, we would like this
> decision to be cost-based. We could use a simple heuristic that would work
> fine for most of the cases without introducing regressions for existing
> cases, e.g., if NDV for partition column is less than estimated parallelism
> in the second RS, do not execute deduplication.
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