How to implement composite primary keys in rails

Question

I have a model Userthat looks like this:

class User < ApplicationRecord
  belongs_to :organization
  belongs_to :department
end

The table usersin the database has two foreign keys organization_idand department_id. How can I make these two columns a composite primary key? So far I have seen two approaches:

Option 1

Use composite_primary_keysgem

Option 2

Add an index to each of the two columns using something like this:

add_index :users, [:organization_id, :department_id], unique: true

My question

What is the best way to uniquely identify rows in a table users, where the line should be department_idand organization_idto uniquely identify? What is the difference between indexing both columns and just turning each column into the primary key of the table?

Thank!

Answer 1

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