So, I do a SHOW PROCESSLIST command in phpMyAdmin, and it shows a ton of SELECT statements that have EXPLAIN in front of every one of them! Now, I never even heard of the EXPLAIN keyword, so I certainly didn’t do it.
It took me a couple hours to figure out, but PHP was putting it there. I had turned mysql.trace_mode = On because the comments said it would give me warnings to table/index scans. It did give me a couple warnings where I didn’t call mysql_free_result(), so I was happy with it. But apparently it also added EXPLAIN to all SELECT statements in order to get some data out of that. Well, I don’t want to slow down the database, so I turned that off. Good to know it’s there I guess, and exactly what it does.
