(Rails) When to use ActiveRecord's .where and .select

I have a Model in my Rails app named User, which has an attribute name

Let's say I want to find all Users whose name matches a specific string.

In a Rails Console, I could do:

OPTION 1

User.where("name LIKE 'string'")

This is very fast.

OPTION 2

User.select{|u| u.name == "string"}

This is extremely slow. It works for a small database, but if you have hundreds of thousands of users, this appears to try to load all Users into memory first, and then iterate them in the block.

Does this mean that option 2 is always wrong ? What's the correct use case for .select then, when is it preferable over .where ?

I wrote a bunch of code in my app that is working fine using .select, but now that I tried using over a very large table I saw that I might be doing something wrong.