Why I could not alter the variable long_query_time variable at runtime
You are setting a GLOBAL system variable, but you querying for the SESSION variable. For the GLOBAL variable setting to take effect for the current session, you need to reconnect, or set the @@SESSION.long_query_time variable. (Note that SHOW VARIABLES by default shows the session variables.) Here is an example: mysql> SHOW SESSION VARIABLES LIKE “long_query_time”; … Read more