How can I optimize complex ActiveRecord queries in Rails 7 for better performance?
I'm maintaining legacy code that I'm experimenting with Setting up a Rails 7 application with a PostgreSQL backend, I've found that some of my ActiveRecord queries are performing poorly, especially those involving multiple joins and subqueries. For example, I have a query that fetches users along with their associated posts and comments. The current implementation looks like this: ```ruby User.includes(posts: :comments).where(active: true).order('created_at DESC') ``` Despite using eager loading, the query still seems to lag when executed on larger datasets. After profiling, it becomes evident that the N+1 query problem persists, particularly with nested associations. I’ve tried rewriting the query using `joins` instead of `includes`, which brought some performance improvement, but it’s still not where I want it to be. Here’s what I attempted: ```ruby User.joins(posts: :comments).where(active: true).order('created_at DESC').select('users.*, posts.*, comments.*') ``` This helped in reducing the number of queries, but it resulted in more data being fetched than necessary, complicating the handling of the response. Additionally, I’ve implemented database indexing on the `created_at` and `active` fields, but the speed improvement was marginal. I'm considering caching strategies or using SQL views for some of the more complex queries. Has anyone had success with caching the results of such queries or perhaps using a different approach such as scopes to break the query into smaller components? If so, what patterns did you find effective? Any insights into optimizing these ActiveRecord queries for performance would be greatly appreciated. I recently upgraded to Ruby stable. I'd really appreciate any guidance on this.