It's not Ruby that's slow, it's your database

That's... weird advice. I think a lot of what happens in Rails projects (based on my very limited experience) is that developers start to rely on this easy syntax that ActiveRecord provides and stop thinking about the queries that the ORM is creating. So you end up with these massive N+1 queries that kill performance.

This is one of the reasons I like to stay away from ORMs at all costs. A majority of what an ORM provides can be solved by a view or a function.

As to Ruby's performance... yeah... it's pretty terrible. We had to completely abandon Docker for Ruby on Rails because the performance was absolutely abysmal, even with VirtioFS enabled.

> Ironically, the performance issue becomes less articulated in this non-http, non-rails context, yet in these cases people generally dismiss ruby as option, for its performance-issues. Which, catch-22, is one of the reasons Ruby is hardly used outside of Rails (and/or Web).

It's a shame that most people only write Ruby in the context of Rails. It's a lovely language, and performant enough for a wide array of tasks. It can be startlingly elegant and exceedingly productive.

Of course, it's valid to talk about Ruby performance in the context of Rails, as the author does. However, it's gratifying to see a more detailed discussion on what Ruby folks mean when they say "your database is usually the bottleneck," and the author does a good job at examining different aspects.

(All that said: Rails is still a really good choice. So much of our work is just writing CRUD apps, and it's kinda boring. Rails makes it boring and easy, and it's a really good tradeoff.)

How would we do this in an ORM like ActiveRecord or Django ORM, without generating multiple queries?

The default ORM in Ruby… not great at scale.

I had a large client with moderate traffic, they were slow because they were absolutely crushing their DB. Now granted it was not JUST ruby, but ruby was a big part of it. We profiled their slow queries and found stuff no human would think is sane.

Active record is great for the developer and terrible for database optimization. Which is fine until you try to scale. Then you fall over on your face.

Ruby is slow because it constructs retarded database queries that no human would ever use. Think ten lines long and multiple joins.