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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-15397) metadata-only queries may return incorrect results with empty tables
Date Sat, 10 Dec 2016 01:17:58 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15397?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15736905#comment-15736905
] 

Sergey Shelukhin commented on HIVE-15397:
-----------------------------------------

Btw, I am too lazy to rerun it again now, but I think the current master is inconsistent,
cause the out file changes that removed the rows on the first run removed the rows because
I disabled metadata-only by default. So, non-optimized path on master doesn't return such
rows, but metadata-only does return them. After the patch, neither does.

> 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-15397.01.patch, 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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