sql_mode=ORACLE: Functions with no parameters can be called without parentheses

When running with sql_mode=ORACLE, MariaDB should allow calling stored functions that have no parameters without having to type parentheses after the function name.

DROP FUNCTION f1;

CREATE FUNCTION f1 RETURN INT

AS

BEGIN

  RETURN 10;

END;

/

SELECT f1 FROM DUAL;

SELECT f1() FROM DUAL;

Notice, the above two SELECT queries return the same result:

SQL> 

	F1

----------

	10

SQL> 

      F1()

----------

	10

Name resolution will follow Oracle rules. For example, table columns shadow stored functions:

DROP FUNCTION f1;

CREATE FUNCTION f1 RETURN VARCHAR

AS

BEGIN

  RETURN 10;

END;

/

DROP TABLE t1;

CREATE TABLE t1 (f1 INT);

INSERT INTO t1 VALUES (20);

SELECT f1 FROM t1;

SQL> 

	F1

----------

	20

Notice, it returned the value of the column t1.f1 rather than the function f1.

Under terms of this task we'll also allow calling SP control functions SQLCODE and SQLERRM with empty parentheses:

DROP FUNCTION f1;

CREATE FUNCTION f1 RETURN INT

AS

BEGIN

  EXECUTE IMMEDIATE 'xxx';

  RETURN 0;

EXCEPTION

  WHEN OTHERS THEN RETURN SQLCODE();

END;

/

SELECT f1 FROM DUAL;