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https://issues.apache.org/jira/browse/CALCITE-695?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14524459#comment-14524459
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Julian Hyde commented on CALCITE-695:
-------------------------------------
I added some tests for scalar sub-queries in
https://git1-us-west.apache.org/repos/asf?p=incubator-calcite.git;a=blob;f=core/src/test/resources/sql/scalar.oq;h=103df2926309e18d380b2bff1e89875ba6287086;hb=f107218b956a1b25d11c8d06c6378bdd22c75378
so I think we're good.
> Do not add SINGLE_VALUE aggregate function to a sub-query that will never
> return more than one row
> --------------------------------------------------------------------------------------------------
>
> Key: CALCITE-695
> URL: https://issues.apache.org/jira/browse/CALCITE-695
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.3.0-incubating
> Reporter: Aman Sinha
> Assignee: Julian Hyde
> Fix For: 1.3.0-incubating
>
>
> In the following query, the subquery is producing a scalar value but the
> logical plan still creates a SqlSingleValueAggFunction.
> {code}
> select r_regionkey from region
> where r_regionkey > (select min(n_regionkey) * 2 from nation);
> {code}
> If the aggregate is just min(n_regionkey) instead of the expression
> min(n_regionkey) * 2 then no SqlSingleValueAggFunction is created. Ideally,
> both should behave the same.
> This is not necessarily a bug but it does create a burden on the underlying
> execution engine to support this function even in cases where it may not be
> needed.
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