Re:[DISCUSS] Allow calling UDFs without parentheses in Calcite

[Kirill Tkalenko]

Hi,

Thanks, your suggestion makes sense, and I like this approach.

We could add allowUdfCallsWithoutParentheses to 
CalciteQueryEngineConfiguration, defaulting to false.
 
It could also apply to parameterless table functions:

SELECT * FROM TABLE(my_function);

For name resolution, I suggest giving columns precedence over UDFs with the 
same name, as Oracle does. 
Explicit parentheses would still allow an unambiguous function call.