Define a unique primary key based on 2 columns

Question

I would like to define a unique key for records based on 2 columns : \'id\' and \'language\'

to let the user submits the following strings : id=1 language=en value=bl

Answer 1

In Rails 5 you can do the following:

create_table :words, primary_key: %i[id language_id] do |t|
  t.integer :id
  t.integer :language_id
  t.string :value
  t.timestamps
end

It is also NOT necessary to set the primary_key attribute on the Word model.