The discussion, titled “Destroy all permalinks” under the Sysadmins category, focuses on efficiently removing old permalinks to improve performance by reducing 404 errors. pfaffman shares a method using Rails console commands to destroy all permalinks, noting a potential 20ms improvement per 404. elijah humorously reacts to the performance claim, while zogstrip suggests using Permalink.destroy_all, which pfaffman confirms he had overlooked, humorously acknowledging the lesson learned.
If you think that only search engines have links to your old URLs, the search engine databases have been updated, and you want to save as much as 20ms on every 404, you can do this:
cd /var/disourse/
./launcher enter app
rails c
Permalink.destroy_all
exit
exit
Thanks to @zogstrip for pointing out the obvious (once you know it)!
Woohoo! That’s really selling it.
Have you tried Permalink.destroy_all? 
No! (obviously). I tried permutations of Permalink.destroy and Permalink.something.destroy.
Public humiliation is a good way to remember things, though, so I think I’ve got this one down now. 