[DRILL-6376] Doc: Return type of ROUND(x, y), TRUNC(x, y), TO_NUMBER is wrong

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.13.0
• Labels: doc-impacting
• Assignee: Bridget Bevens
• Reporter: Paul Rogers
• Created: 02/May/18 05:14
• Updated: 02/May/18 05:14

Description

The documentation for math functions claims that the return value of ROUND(x, y) and TRUNC(x, y) is DECIMAL. A test shows that this is not true:

SELECT typeof(ROUND(a, 2)) FROM (VALUES (1.2345)) AS T(a);
+---------+
| EXPR$0  |
+---------+
| FLOAT8  |
+---------+
SELECT typeof(TRUNC(a, 2)) FROM (VALUES (1.2345)) AS T(a);
+---------+
| EXPR$0  |
+---------+
| FLOAT8  |
+---------+

Maybe it is DECIMAL only if we enable decimal type? Let's try:

ALTER SESSION SET `planner.enable_decimal_data_type` = true;
SELECT typeof(TRUNC(a, 2)) FROM (VALUES (1.2345)) AS T(a);
+---------+
| EXPR$0  |
+---------+
| FLOAT8  |
+---------+

So, ROUND() and TRUNC() actually return DOUBLE.

The type convertion documentation says that TO_NUMBER(str, fmt) returns DECIMAL. Let's try:

ALTER SESSION SET `planner.enable_decimal_data_type` = true;
SELECT typeof(TO_NUMBER(a, '0')) FROM (VALUES ('1')) AS T(a);
+---------+
| EXPR$0  |
+---------+
| FLOAT8  |
+---------+

So, TO_NUMBER() actually returns DOUBLE.