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https://issues.apache.org/jira/browse/CALCITE-4702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17457171#comment-17457171
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Stamatis Zampetakis commented on CALCITE-4702:
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There is no significant benefit in treating Redshift and Postgres differently.
I was mostly concerned by the fact that it can be weird for someone who will
encounter this API in the future (thinking that it is wrong) but this can be
solved with some good javadoc. Moreover, having {{GROUP BY}} and literals
should not be very frequent use-case thus I agree with Julian that probably
does not worth the extra complexity.
> Error when executing query with GROUP BY constant via JDBC adapter
> ------------------------------------------------------------------
>
> Key: CALCITE-4702
> URL: https://issues.apache.org/jira/browse/CALCITE-4702
> Project: Calcite
> Issue Type: Bug
> Components: core, jdbc-adapter
> Affects Versions: 1.27.0
> Reporter: Stamatis Zampetakis
> Assignee: Soumyakanti Das
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 10m
> Remaining Estimate: 0h
>
> The following functionally equivalent SQL queries are accepted by Calcite and
> produce a valid plan
> {noformat}
> select avg(salary) from employee group by true
> select avg(salary) from employee group by 'a'
> {noformat}
> but they may fail if they are executed via the JDBC adapter since not all
> DBMS allow grouping by constants expressions. Moreover, what works for one
> may not work for the other.
> +Examples+
> The {{GROUP BY TRUE}} query works in Postgres, and MySQL but fails in
> Redshift with the following exception:
> {noformat}
> com.amazon.redshift.util.RedshiftException: ERROR: non-integer constant in
> GROUP BY
> {noformat}
> The {{GROUP BY 'a'}} query works in MySQL but fails in Postgres with the
> following exception:
> {noformat}
> ERROR: non-integer constant in GROUP BY
> {noformat}
> +Edit:+
> The {{GROUP BY}} constant is similar to {{GROUP BY ()}} "nothing" but as
> shown in the discussion below they are not equivalent. There is a nice [blog
> post|https://blog.jooq.org/2018/05/25/how-to-group-by-nothing-in-sql/]
> listing some limitations of various DBMS when it comes to {{GROUP BY ()}}.
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