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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