Bug #34878 Few variables have default value according to documentation but error occurs
Submitted: 27 Feb 2008 10:53 Modified: 16 Mar 2010 0:02
Reporter: Salman Rawala Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: DML Severity:S3 (Non-critical)
Version:5.1.22, 5.1.23 OS:Any
Assigned to: CPU Architecture:Any
Tags: Invalid default value

[27 Feb 2008 10:53] Salman Rawala
Description:
There are few variables that are giving errors on assigning DEFAULT value to variable, but according to documentation, they have default value. These variales are:

max_connect_errors, max_connections, delay_key_write, log_output, flush, key_buffer_size, key_cache_age_threshold, key_cache_block_size, key_cache_division_limit, max_binlog_size
g

How to repeat:
Sample Code:
SET @@global.key_buffer_size = 99;
--Error ER_NO_DEFAULT
SET @@global.key_buffer_size = DEFAULT;

Actual Output:
SET @@global.key_buffer_size = 99;
SET @@global.key_buffer_size = DEFAULT;
ERROR 42000: Variable 'key_buffer_size' doesn't have a default value
[27 Feb 2008 11:15] Valeriy Kravchuk
Indeed, some of these variables does NOT accept DEFAULT as value.
[7 Aug 2009 14:33] Sergei Golubchik
will be fixed in WL#4738
[6 Mar 2010 11:03] Bugs System
Pushed into 5.5.3-m3 (revid:alik@sun.com-20100306103849-hha31z2enhh7jwt3) (version source revid:vvaintroub@fedora12-20091225154921-x25a5pyw1pxiwobv) (merge vers: 5.5.99) (pib:16)
[16 Mar 2010 0:02] Paul Dubois
Noted in 5.5.3 changelog.

Some system variables could not be assigned the value DEFAULT to
assign their default value.