The Sillican Files » php http://blog.sillica.com Computers, Games, and Life Randomness Mon, 19 Jul 2010 14:28:56 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 Why is the word EXPLAIN in front of every MySQL query in SHOW PROCESSLIST? http://blog.sillica.com/2008/07/04/why-is-the-word-explain-in-front-of-every-mysql-query-in-show-processlist/ http://blog.sillica.com/2008/07/04/why-is-the-word-explain-in-front-of-every-mysql-query-in-show-processlist/#comments Fri, 04 Jul 2008 02:28:17 +0000 Erick http://blog.sillica.com/?p=538 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.

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