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https://issues.apache.org/jira/browse/HIVE-27831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ramesh Kumar Thangarajan resolved HIVE-27831.
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Fix Version/s: 4.1.0
Resolution: Fixed
Thank you [~zabetak] and [~soumyakanti.das] for the PR and review and all the
related work to get this in.
> Set hive.cbo.fallback.strategy to NEVER by default
> --------------------------------------------------
>
> Key: HIVE-27831
> URL: https://issues.apache.org/jira/browse/HIVE-27831
> Project: Hive
> Issue Type: Task
> Components: CBO
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.1.0
>
>
> The hive.cbo.fallback.strategy property defines when Hive fallbacks to legacy
> optimizer if an error occurs during the CBO phase.
> At the moment the default value is CONSERVATIVE, which is the backward
> compatible option, and automatically fallbacks to legacy optimizer when
> certain errors occur.
> The legacy optimizer is (hive.cbo.enable=false) is gonna soon be officially
> deprecated (HIVE-27830); unofficially it was treated as such for a long time
> now.
> To reduce maintenance cost and improve CBO coverage and stability we should
> NEVER fallback to the legacy optimizer after a CBO error.
> NEVER should be the default behavior in newer releases; users can still set
> the property to CONSERVATIVE as a temporary workaround till the CBO error is
> addressed.
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