Actually both lock for many (crucial) schema operators, and often severely enough to block your application from reading from the table(s) under change. I've be

Actually both lock for many (crucial) schema operators, and often severely enough to block your application from reading from the table(s) under change. I've been researching this stuff for a while. Check out http://blog.minicom.nl/blog/2015/04/03/revisiting-profiling-ddl-statements-mysqls-return/ http://blog.minicom.nl/blog/2015/04/03/revisiting-profiling-... . It's slightly outdated, but still holds.