MySQL Caching

Question

Last night I added a parameter to a stored procedure in a mySQL database. I accessed it, messed up the parameter, and decided to remove the parameter again, for testing. Still minutes after re-creating the procedure without the parameter, my command object was still complaining about a missing parameter. Is this mySQL, MySQL/Connector, ADO, or Enterprise library's fault, and what can I do about it?

Answer 1

By default MySQL caches queries in your stored procedures. See if Query Cache is enabled:

SHOW VARIABLES LIKE 'query_cache%'

Stored procedure calls are not cached by MySQL, but if query_cache_type is ON this will affect caching of queries issued from within the procedure. Possibly causing MySQL to return the same results for a couple of minutes. Try flushing the cache, or better yet, reset the query cache to remove all queries if your updated procedure keeps returning the previous result set:

RESET QUERY CACHE 

That should eliminate any caching by MySQL server.

Next time this happens you could execute the procedure by hand through another tool that does not use MySQL/Connector or Enterprise Library. That will tell you if the old result set is cached by either MySQL or the drivers and application blocks in your application.

Edit: please read the comments below, by desertwebdesign. After recreating the sproc, drop the connection. Connection pooling may keep the connection open, so it's probably best to kill the connection from MySQL. Most query browsers have a tab that allow you to kill connections in MySQL if you log in with process/super privileges.

SHOW FULL PROCESSLIST
KILL CONNECTION thread_id