[jira] [Created] (CALCITE-4702) Error when executing query with GROUP BY constant via JDBC adapter

["Stamatis Zampetakis (Jira)" <ji...@apache.org>]

Stamatis Zampetakis created CALCITE-4702:
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             Summary: 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: Stamatis Zampetakis


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}

The {{GROUP BY}} constant essentially means {{GROUP BY}} nothing and 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. 



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