Turning on and off Switchable optimizations

I have to turn off derived_merge optimization flag because of this issue, so I do it like from the link above:

set global optimizer_switch='derived_merge=OFF';

but also I would like to check its current value... How can I do that through the command line ?

Ah, I just found it in official docs :)

Here is how you do it:

mysql> SELECT @@optimizer_switch\G