I know you're not supposed to do this, but I have a MySQL 5.5 master and a MySQL 5.1 replication slave. That's supposed to be okay, unless I do something stupid like use utf8mb4 that isn't supported by 5.1. Well, everything has been going well for a while and today I got a replication slave failure because character_set_client #45 isn't supported by MySQL 5.1.
I spent a lot of time trying to find out what #45 was... you see, it doesn't appear in any of MySQL's configuration files -- even on 5.5. I finally determined it was utf8mb4 (which I had suspected) but I'm not sure why it's being used. I performed a static query on the master ... something simple like
UPDATE table SET field='value' and it replicated to the slave by setting the character set to utf8mb4. I executed hundreds of similar
UPDATE statements at the same time, but some of them triggered the use of utf8mb4.
So... I'm going to be upgrading my slave to 5.5, but in the mean time is there a way to tell MySQL to never use utf8mb4?