Unexpected performance implementing ActiveRecord queries in Rails 7 with PostgreSQL
I've tried everything I can think of but Quick question that's been bugging me - I'm experiencing important performance optimization when executing certain ActiveRecord queries in my Rails 7 application using PostgreSQL... For example, I have a query that fetches users along with their associated posts, but it's taking an unusually long time to complete. Here’s the code snippet I’m using: ```ruby users = User.includes(:posts).where(active: true).order('created_at DESC').limit(100) ``` When I run this query, it sometimes takes more than 5 seconds, which is unacceptable for my application. I’ve checked the database logs, and I noticed that it’s performing a sequential scan instead of using an index, which seems to be the root of the scenario. I have an index on `posts.user_id`, but it doesn’t seem to be utilized here. I’ve tried a few things to diagnose the question: 1. I used `EXPLAIN ANALYZE` in PostgreSQL to see the query plan, and it shows that the index is not being used because of the `WHERE` clause. 2. I also experimented with using `joins` instead of `includes`, but that resulted in an even slower query, due to the resulting larger dataset. 3. Ensured that I optimized the database by running `VACUUM ANALYZE`, but it didn’t help. Is there a way to optimize this query further or any best practices to follow to avoid performance pitfalls with ActiveRecord in Rails 7? Any help would be greatly appreciated. Any ideas what could be causing this? I'm open to any suggestions. For reference, this is a production mobile app. Could this be a known issue?