From: Rik Wasmus
Date: July 7 2012 5:34am
Subject: Re: Subquery taking too much time on 5.5.18?
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> See "The unbearable slowness of IN()" at
> http://www.artfulsoftware.com/infotree/queries.php


Do you read your own links? Excerpt:

> In 5.0, EXISTS() is much faster than IN(), but slower than JOIN. In 5.5, 
EXISTS() performs about as well as JOIN.

So.... judging by the subject line...