MySQL Bugs: #61224: function pow is wrong

Bug #61224	function pow is wrong
Submitted:	19 May 2011 10:13	Modified:	23 May 2011 1:45
Reporter:	YanHui Wang	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: DML	Severity:	S3 (Non-critical)
Version:	5.5.12	OS:	Windows (XP)
Assigned to:		CPU Architecture:	Any
Tags:	pow, regression

Description:
function POWER(X,Y) 

when X is negative number, the function pow is wrong.

How to repeat:
function POWER(X,Y) 

when X is negative number, the function pow is wrong.

Can you give specific example of wrong value returned? I do not see any problem:

mysql> select power(2,3);
+------------+
| power(2,3) |
+------------+
|          8 |
+------------+
1 row in set (0.11 sec)

mysql> select power(-2,3);
+-------------+
| power(-2,3) |
+-------------+
|          -8 |
+-------------+
1 row in set (0.02 sec)

The SQL below run in MySQL Community Server 5.5.12,
select pow(-1, 1/2);

Error Code: 1690
DOUBLE value is out of range in 'pow(-(2),(1 / 2))'

if the SQL run in MySQL Community Server 5.1, it is OK.

Indeed, in 5.1.x we get NULL (there is no real number as a result of pow(-1, 1/2)), while in 5.5 we get error message that looks misleading:

macbook-pro:5.5 openxs$ bin/mysql -uroot test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.15-debug Source distribution

Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select pow(-2, (1/2));
ERROR 1690 (22003): DOUBLE value is out of range in 'pow(-(2),(1 / 2))'
mysql> select pow(-1, 1/2);
ERROR 1690 (22003): DOUBLE value is out of range in 'pow(-(1),(1 / 2))'

Thanks for your reply.

Posted by developer:
 
Reporting an error is in this case is correct according to SQL standard.
However, the error message is misleading and could be improved.