Why don't Ruby developers like to create indexes on databases?

Question

Ruby on Rails

I'm reading a book - "7 Databases in 7 weeks", Eric Redmond
There I met this:

I also found a similar statement on the ibm.com website:

While most Rails developers don't like to set limits on the database itself, you still need to consider things like

What's the catch? Can you explain why Ruby developers are so reluctant to create indexes on columns ?

Answer 1

This is a joke caused by the extremely low level of entry into the Ruby on Rails ecosystem.
The author of the book rudely teases the average inexperienced RoR developer by shifting the focus to the tool. This is acceptable in a friendly conversation, but in a book it looks dirty.

Answer 2

Oh yes, this is a fundamental problem with any ORM tool - by encapsulating the specifics of storage, they create the illusion of ease of working with RDBMS.
It really works for simple cases (little data, few queries, simple domain). And this is very relaxing for the developer.
Serious work with the database can never come from the ORM tool, only from the database itself, and then there are indexes of all stripes, partitioning and all sorts of other access / storage optimization tricks.
The illusions of an ORM-driven design are shattered, leading to tasks like "everything needs to be redone!" This is what the author hints at, saying that life is a little more complicated than it seems.