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https://issues.apache.org/jira/browse/HIVE-27830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18033340#comment-18033340
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Denys Kuzmenko commented on HIVE-27830:
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[~zabetak] should we remove the config in 4.2?
> Deprecate hive.cbo.enable property
> ----------------------------------
>
> Key: HIVE-27830
> URL: https://issues.apache.org/jira/browse/HIVE-27830
> Project: Hive
> Issue Type: Task
> Reporter: Stamatis Zampetakis
> Assignee: Stamatis Zampetakis
> Priority: Major
>
> CBO was enabled by default in Hive 1.1.0 (HIVE-8395) back in 2014. Since then
> the CBO planner has matured a lot and most production environments are
> running with this flag always on.
> Nowadays, disabling CBO is strongly discouraged not only for performance
> reasons but also because various features depend on it.
> Moreover, the vast majority of testing is done using CBO on and there is not
> much test coverage for the legacy code path.
> It is impossible to fully support all Hive features using both CBO on/off and
> keeping this flag around significantly increases maintenance cost.
> The goal of this ticket is to deprecate hive.cbo.enable property and inform
> users that its use is discouraged and unsupported. This would allow us to
> remove this property in a subsequent release.
> Ideally we should emit an informative warning message when we detect that
> hive.cbo.enable is set to false.
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