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Posted to issues@hive.apache.org by "Simhadri Govindappa (Jira)" <ji...@apache.org> on 2023/01/31 10:13:00 UTC

[jira] [Assigned] (HIVE-27005) Iceberg: Col stats are not used in queries

     [ https://issues.apache.org/jira/browse/HIVE-27005?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Simhadri Govindappa reassigned HIVE-27005:
------------------------------------------

    Assignee: Simhadri Govindappa

> Iceberg: Col stats are not used in queries
> ------------------------------------------
>
>                 Key: HIVE-27005
>                 URL: https://issues.apache.org/jira/browse/HIVE-27005
>             Project: Hive
>          Issue Type: Improvement
>          Components: Iceberg integration
>            Reporter: Rajesh Balamohan
>            Assignee: Simhadri Govindappa
>            Priority: Major
>              Labels: iceberg, performance
>         Attachments: col_stats.txt
>
>
> 1. Though, insert-queries compute colstats during runtime, they are not persisted in HMS during final call. 
> 2. Due to #1, col stats are not available during runtime for hive queries. This includes col stats, NDV etc. So unless users explicitly run "analyse table" statements, queries can be have suboptimal plans.
> E.g [col_stats.txt{^}!https://jira.cloudera.com/images/icons/link_attachment_7.gif|width=7,height=7!{^}|https://jira.cloudera.com/secure/attachment/658390/658390_col_stats.txt](note that there is no col stats being used)



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