스칼라 JavaScript UDFs¶

CREATE OR REPLACE FUNCTION RECURSION_TEST (STR VARCHAR)
  RETURNS VARCHAR
  LANGUAGE JAVASCRIPT
  AS $$
  return (STR.length <= 1 ? STR : STR.substring(0,1) + '_' + RECURSION_TEST(STR.substring(1)));
  $$
  ;

SELECT RECURSION_TEST('ABC');
+-----------------------+
| RECURSION_TEST('ABC') |
|-----------------------|
| A_B_C                 |
+-----------------------+

CREATE FUNCTION validate_ID(ID FLOAT)
RETURNS VARCHAR
LANGUAGE JAVASCRIPT
AS $$
    try {
        if (ID < 0) {
            throw "ID cannot be negative!";
        } else {
            return "ID validated.";
        }
    } catch (err) {
        return "Error: " + err;
    }
$$;

CREATE TABLE employees (ID INTEGER);
INSERT INTO employees (ID) VALUES 
    (1),
    (-1);

SELECT ID, validate_ID(ID) FROM employees ORDER BY ID;
+----+-------------------------------+
| ID | VALIDATE_ID(ID)               |
|----+-------------------------------|
| -1 | Error: ID cannot be negative! |
|  1 | ID validated.                 |
+----+-------------------------------+