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https://issues.apache.org/jira/browse/HIVE-19489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16471762#comment-16471762
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Zoltan Haindrich commented on HIVE-19489:
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I'm not sure if we should disable it globally; but there could be an option to
do that - I think it would be probably be usefull to have a table level option
to prevent it from happening on specific tables. Without statistics the planner
will start operating in blind: I think fs level stats are not really good; auto
gathering may also collect column stats which could be very usefull during
estimations.
afaik auto gathering should not happen during LOAD DATA statements
cc: [~ashutoshc]
> Disable stats autogather for external tables
> --------------------------------------------
>
> Key: HIVE-19489
> URL: https://issues.apache.org/jira/browse/HIVE-19489
> Project: Hive
> Issue Type: Sub-task
> Components: Statistics
> Reporter: Jason Dere
> Assignee: Jason Dere
> Priority: Major
>
> Hive auto-gather of table statistics can result in incorrect generation of
> stats (and the stats being marked as accurate) in the case of external tables
> where the data is being written by external apps.
> To avoid this issue, stats autogather will be disabled on external tables
> when loading/inserting into a table with existing data, if
> HIVE_DISABLE_UNSAFE_EXTERNALTABLE_OPERATIONS is enabled. In this situation,
> users should rely on explicitly calling ANALYZE TABLE on their external
> tables to make sure the stats are kept up-to-date.
> Autogather of stats will still be allowed to occur on external tables in the
> case of INSERT OVERWRITE or LOAD DATA OVERWRITE, since the existing data is
> being removed and so the stats calculated on the inserted/loaded data should
> be accurate.
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