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From "Vineet Garg (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-16330) Improve plans for scalar subquery with aggregates
Date Wed, 29 Mar 2017 23:08:41 GMT
Vineet Garg created HIVE-16330:
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             Summary: Improve plans for scalar subquery with aggregates
                 Key: HIVE-16330
                 URL: https://issues.apache.org/jira/browse/HIVE-16330
             Project: Hive
          Issue Type: Improvement
            Reporter: Vineet Garg
            Assignee: Vineet Garg


Scalar subquery plans are generated with a count(*) on subquery which is fed to {{sq_count_check}}
UDF. This is to make sure at runtime that there is at most one row generated by scalar subquery.


We can avoid generating this extra count(*) for scalar subqueries with aggregates and windowing
since such queries are guaranteed to generate at most one row. e.g. {code:SQL} select * from
part where p_size > (select max(p_size) from part) {code}



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