We are doing a book club on this and came across the same issue

In PostgreSQL, data is laid out in pages. Data cannot be split across pages. Data is stored efficiently when there are minimal gaps and data that is accessed resides within a single page. Data that’s in a single page requires fewer disk operations compared with accessing data that is split across multiple pages.

Do you have additional comments I can share with the club?

Hi @andatki ,
Thanks for the explanation, it is much appreciated. So far I’m quite pleased with your book and I’ll be happy to provide constructive feedback if I’ll spot anything else.
Cheers

Thank you @andatki

We have 8 members right now. Our goal is to cover 1 chapter a week and we meet every other week. Our next session will cover chapters 3 & 4.

With regards to specific topics, we have some intense queries in our app and would love to find ways to optimize them. Many are written in custom SQL and we are also trying to push them more into ActiveRecord queries. Any tips on leveraging less known ActiveRecord features that can help with performance would be extremely helpful.