Lemmy Server Performance

420 readers

1 users here now

lemmy_server uses the Diesel ORM that automatically generates SQL statements. There are serious performance problems in June and July 2023 preventing Lemmy from scaling. Topics include caching, PostgreSQL extensions for troubleshooting, Client/Server Code/SQL Data/server operator apps/sever operator API (performance and storage monitoring), etc.

founded 1 year ago

MODERATORS

[email protected]

231

GREAT NEWS about Lemmy Server Performance, another major SQL mistake has been discovered today: every single comment & post create (INSERT) is updating ~1700 rows in the site_aggregates table (lemmy.ml)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]

27 comments fedilink hide all child comments

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! ;)

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 11 points 1 year ago

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.