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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HIVE-15397) metadata-only queries may return incorrect results with empty tables
Date Fri, 09 Dec 2016 01:07:58 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15733912#comment-15733912
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Sergey Shelukhin edited comment on HIVE-15397 at 12/9/16 1:07 AM:
------------------------------------------------------------------

See follow-up.
In that case you might as well just add the limit to original table scan and not use NullScan,
cause it's no longer a nullscan.
That will also require running a task, split generation etc., so it may be involved.


was (Author: sershe):
See follow-up.
In that case you might as well just add the limit to original table scan and not use NullScan,
cause it's no longer a nullscan

> metadata-only queries may return incorrect results with empty tables
> --------------------------------------------------------------------
>
>                 Key: HIVE-15397
>                 URL: https://issues.apache.org/jira/browse/HIVE-15397
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>         Attachments: HIVE-15397.patch
>
>
> Queries like select 1=1 from t group by 1=1 may return rows, based on OneNullRowInputFormat,
even if the source table is empty. For now, add some basic detection of empty tables and turn
this off by default (since we can't know whether a table is empty or not based on there being
some files, without reading them).



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