[CALCITE-5261] UNION(ALL) inside of the CURSOR throws an exception while validating the query

[xuzifu666]

jira: https://issues.apache.org/jira/browse/CALCITE-5261

[mihaibudiu]

This part is not obvious to me, and it does not have coverage in the tests. Can it be reached? Could you also reduce the set case in the same way?

[xuzifu666]

Thanks for the suggestion. Here was reachable and in fact contained a bug: for a query like cursor(values ('a'), ('b')), it would hit the else branch and throw ClassCastException because of the cast (SqlSelect) query.

I refactored the code to handle the non-SELECT cases explicitly:

1. SELECT keeps the original SelectScope + SelectNamespace behavior.
2. UNION/INTERSECT/EXCEPT now use a ListScope + SetopNamespace.
3. VALUES uses TableConstructorNamespace.
4. WITH uses WithNamespace.
5. Anything else throws Util.unexpected(...) (because can not use real sql to cover this condition).

Regarding reducing the set case the same way: I tried using parentScope directly for SET_QUERY, but it fails because parentScope is often a DelegatingScope, whose addChild throws UnsupportedOperationException. So the ListScope maybe still needed.

I also added test coverage for all branches in SqlValidatorTest.testCollectionTableWithCursorParam and a new testDeclareCursorUnexpectedKind.

[mihaibudiu]

Are there any quidem tests with cursor?
(If so, it would be nice to have one, but maybe it's not supported)

[xuzifu666]

Are there any quidem tests with cursor? (If so, it would be nice to have one, but maybe it's not supported)

Yes, That was my plan at first, too. But Maybe there is no way to add a quidem test for CURSOR alone either.

The reason is that CURSOR itself is not executable SQL. It is just a constructor that only makes sense as an argument to a table function. In Calcite, the only built-in function that accepts a CURSOR argument is DEDUP, which is a mock function without an actual execution implementor.

Since quidem is an end-to-end execution test framework:

• Without DEDUP, there is no function to wrap CURSOR(...), so the SQL is not syntactically valid.
• With DEDUP, the execution phase fails because DEDUP has no Enumerable implementor.

I verified earlier that select * from table(dedup(cursor(select ...), 'ENAME')) passes validation and SqlToRel conversion, but fails at execution.

So CURSOR can only be covered in validator / SqlToRel converter unit tests for now, not in quidem. @mihaibudiu

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
96.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[xuzifu666]

Since this pr has been approved, I had squashed the commits. If there are no other comments, I will merge it.