In the process of investigating the performance of using Shredder to delete 
tickets, I found an index that seems to have a considerable improvement on 
performance, even above the indexes that are suggested in the documentation. I 
simply added:

CREATE INDEX SHREDDER_CGM3 ON CachedGroupMembers(Val, Id);

Before, when I had no indexes, deleting 500 tickets (there are ~ 100,000 in our 
database), the process took about 2 hours and 30 minutes. After adding the 
suggested indexes (which I found in the CPAN documentation), the process took 
about 1 hour, 15 minutes. After adding the above index, the process took about 
16 minutes. I stumbled upon this while using the tool mytop (available at 
http://jeremy.zawodny.com/mysql/mytop/).

I am pretty certain that, despite the occasionally self-referrential nature of 
the Val field in the CGM table, this index shouldn't lead to any difference in 
results, ordering, or completeness in deletion. I haven't had the time to 
check, though - so obviously I take no responsibility for any huge catastrophes 
that may occur on your particular database.

Anyway, thanks to Ruslan Zakirov for a great tool.

Cheers,
-Drew Day
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