Aggregate function that returns a type that cannot be Nullable should still be supported for aggregate_functions_null_for_empty #38786
Description
@Alex-Cheng these functions should return the default value instead of NULL.
Now it's not the case:
SELECT groupArray(x) FROM (SELECT toNullable(1) AS x) SETTINGS aggregate_functions_null_for_empty = 1
Code: 43. DB::Exception: Nested type Array(UInt8) cannot be inside Nullable type. (ILLEGAL_TYPE_OF_ARGUMENT)
And should be improved.
Originally posted by @alexey-milovidov in #10273 (comment)