mysql user host field in slow query log
Here is one way to know

Login to MySQL and run this

SELECT USER(),CURRENT_USER(); SELECT SLEEP(15);


What will this tell you ?


USER() reports how you attempted to authenticate in MySQL
CURRENT_USER() reports how you were allowed to authenticate in MySQL


Look for the SELECT SLEEP(15); query in the slow log. From there, you should be able to tell whether USER() or CURRENT_USER() was used to set # User@Host:.