SHOW VARIABLES Shows Variables MySQL Does Not Know About
Jan 8, 2008 / By Sheeri Cabral
The listing of Dynamic System Variables on the MySQL Reference Manual’s page is supposed to show those variables you can change on-the-fly.
innodb_data_home_dir is listed there as a dynamic variable, but it is not one, and trying to change it on-the-fly doesn’t work:
mysql> set global innodb_data_home_dir="/data/mysql/data"; ERROR 1193 (HY000): Unknown system variable 'innodb_data_home_dir' mysql> set session innodb_data_home_dir="/data/mysql/data"; ERROR 1193 (HY000): Unknown system variable 'innodb_data_home_dir'
The same goes when trying to use
SET @@innodb_data_home_dir, and with
log-slow-queries (changed to
log_slow_queries as a parameter, of course). The irony is that
innodb_data_home_dir shows up when
SHOW VARIABLES is issued — so
SHOW VARIABLES shows variables that MySQL is not aware of.
The link at the top is a link to the 4.1 version of the manual, just in case folks are thinking I’m using a newer manual version. Mind you, I have this problem with 5.0.45 as well as 4.1.20.
And of course the manual specifies, “The last column indicates for each variable whether
SESSION (or both) apply.” Which seems to be untrue.
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