Details here: https://github.com/LemmyNet/lemmy/issues/3165
This will VASTLY decrease the server load of I/O for PostgreSQL, as this mistaken code is doing writes of ~1700 rows (each known Lemmy instance in the database) on every single comment & post creation. This creates record-locking issues given it is writes, which are harsh on the system. Once this is fixed, some site operators will be able to downgrade their hardware! ;)
Ah Gotcha. That’s true, but the cascading issue that causes thousands of inserts happens on a delete.
That table update you’re looking at is blazing fast due to the relatively low number of sites, until you run it thousands of times on a delete.