[development] Good article on MEMORY temp tables in MySQL

[Robert Douglass]

For those of you who like reading performance tuning stuff: 
http://www.mysqlperformanceblog.com/2007/08/16/how-much-overhead-is-caused-by-on-disk-temporary-tables/

This could be particularly relevant to Drupal.org if we are still 
getting temp tables written to disk. It turns out that even when we 
specify MEMORY for temp tables, MySQL still has the option of writing to 
disk if other buffers aren't large enough.

-R