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https://issues.apache.org/jira/browse/HIVE-12640?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hari Sankar Sivarama Subramaniyan updated HIVE-12640:
-----------------------------------------------------
Attachment: HIVE-12640.3.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,
> HIVE-12640.3.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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