Increase in Postgresql CPU usage from Sidekiq

Summary

Since a few days, our Gitlab Postgresql is under heavier load, using twice as much CPU, even when our instance is not used (eg: during out of office hours). It might comes from Sidekiq / Rails.

Stack:

• Kubernetes (EKS) 1.32
• RDS Postgresql 16.8
• GitLab 18.5.1-ee

After a bit of drill-down, I can now pin-point this CPU increase to Sidekiq and to the following request:

SELECT a.attname FROM ( SELECT indrelid, indkey, generate_subscripts(indkey, ?) idx FROM pg_index WHERE indrelid = ?::regclass AND indisprimary ) i JOIN pg_attribute a ON a.attrelid = i.indrelid AND a.attnum = i.indkey[i.idx] ORDER BY i.idx

Relevant logs and/or screenshots

Here is an example where I disable all Cron from Sidekiq, before enabling them back.

Possible fixes

I found an issue and a fix on rails' Github: https://github.com/rails/rails/issues/55648