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From "Hari Sankar Sivarama Subramaniyan (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-12640) Allow StatsOptimizer to optimize the query for Constant GroupBy keys
Date Mon, 14 Dec 2015 18:44:46 GMT

     [ https://issues.apache.org/jira/browse/HIVE-12640?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hari Sankar Sivarama Subramaniyan updated HIVE-12640:
-----------------------------------------------------
    Attachment: HIVE-12640.2.patch

> Allow StatsOptimizer to optimize the query for Constant GroupBy keys 
> ---------------------------------------------------------------------
>
>                 Key: HIVE-12640
>                 URL: https://issues.apache.org/jira/browse/HIVE-12640
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Hari Sankar Sivarama Subramaniyan
>            Assignee: Hari Sankar Sivarama Subramaniyan
>         Attachments: HIVE-12640.1.patch, HIVE-12640.2.patch
>
>
> {code}
> hive> select count('1') from src group by '1';
> {code}
> In the above query, while performing StatsOptimizer optimization we can safely ignore
the group by on the constant key '1' since the above query will return the same result as
"select count('1') from src".
> Exception:
> If src is empty, according to the SQL standard,
> {code}
>  select count('1') from src group by '1'
> {code}
> and
> {code}
>  select count('1') from src
> {code}
> should produce 1 and 0 rows respectively.



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