[jira] [Commented] (HIVE-27831) Set hive.cbo.fallback.strategy to NEVER by default

["Soumyakanti Das (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-27831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17854553#comment-17854553 ] 

Soumyakanti Das commented on HIVE-27831:
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This test is no longer failing in the latest run (http://ci.hive.apache.org/job/hive-precommit/job/PR-5284/1/testReport/):
h3. DirectSQL exception during partition pruning

fname=materialized_view_authorization_sqlstd.q
{code:sql}
explain select * from db1.testmvtable where year=2020 {code}

> 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
>
> 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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