title: Difference between DROP USER and deleting a row from the mysql.user table
body: <p>I have a database with hundreds of active connections at any point in time. When I use the DROP USER sql statement to remove a user account, it takes ~4 seconds, during which all other connections have the state "Checking permissions". This means that to delete 1000 users, I'll effectively be locking the database for a good part of 4000 seconds, which is unacceptable. I do notice, however, that deleting a user row from the mysql.users table is instant.</p>
  
  <p>Is deleting a row from mysql.users kosher? What are the drawbacks compared to using DROP USER? Am I leaving stale rows elsewhere? Are there propagation issues? I'm most likely going to have to go this route, but I want to know what other clean up I'll need to do.</p>