This is really strange, the fact that is is 255 and not 191. I was part of a discussion about raising the limit of option_name to 255 and they decided there that 191 would be better since the index is only capable of indexing 191 characters. I’ve never noticed that the meta_key field allowed 255, or I have, but I did not think about the fact the the index only works on the first 191 characters.
I find it a little amusing that the length of this db field does not consider the max length of the key.
I used to use this to force the length of the options name field to be longer and not allow WP updates to change it. https://github.com/Hube2/wp-update-prevent-db-changes. I’ll need to look forcing the meta_key field to stay at 191.
Thanks for making me aware of this
