Note by @fastfinge

Good grief I wish someone would create a way to do a mass migration from #lemmy to #piefed. Lemmy is by far the most annoying software I have the displeasure of maintaining. In today's adventures, the Lemmy developers finally created a #postgres index in 0.19.15 that I'd created myself ages ago for performance reasons. But the database migration fails if the index already exists. Even if it's the exact index it wants to create, created exactly the way the migration is doing it. And no, you can't skip a database migration, and no, it's not smart enough to check and skip the migration by itself. So you have to log into the database and drop index idx_post_aggregates_creator, and let Lemmy recreate it. Yes, this takes a while, for absolutely no reason. And if you wanted to do it without downtime in an offline copy of the database, I guess you'd have to do a bunch of fiddling to trick Lemmy into thinking the migration happened when you went to upgrade production. There had to be a better way to do that! But it's not documented and I have no idea what it would be.