MySQL Bugs: #11114: wrong rounding in FORMAT() on Windows (test 'func

Bug #11114	wrong rounding in FORMAT() on Windows (test 'func_math' fails)
Submitted:	6 Jun 2005 13:07	Modified:	6 Jun 2005 21:48
Reporter:	Carsten Segieth	Email Updates:
Status:	Duplicate	Impact on me:	None
Category:	MySQL Server	Severity:	S2 (Serious)
Version:	5.0.6-beta	OS:	Windows (Windows XP Home SP2)
Assigned to:		CPU Architecture:	Any

Description:
'perl mysql-test-run.pl func_math' leads to a wrong result on Windows:

select format(4.55, 1), format(4.551, 1);
format(4.55, 1)	format(4.551, 1)
4.5	4.6

where the 1st '4.5' is wrong. It should be (as it seems on Unix?) '4.6'.

How to repeat:
try test case on Windows using the 5.0.6-beta binaries

Please do not submit the same bug more than once. An existing
bug report already describes this very problem. Even if you feel
that your issue is somewhat different, the resolution is likely
to be the same. Because of this, we hope you add your comments
to the original bug instead.

Thank you for your interest in MySQL.

Additional info:

http://bugs.mysql.com/bug.php?id=8459

Just to clarify:

currently FORMAT(X, N) implicitly casts the argument (X) to double. Thus, the rounding rules of the system libc apply, and results become OS- and architecture-dependent.

Fix: FORMAT() should use exact arithmetics when operating with exact numbers.