Rails3: two ways to add index to db table

there is two ways to add index to db table

1. references

if we have two tables , article and commens, the association is 1:M , in order to make search data fast , we should add index to the db table, when we use rails command line to generate the model, you can do it like this

 

rails g model artile title:string 
rails g model comment content:string artile:references

 

then open the generated migration, you'll see

 

class CreateComments < ActiveRecord::Migration
  def change
    create_table :comments do |t|
      t.string :content
      t.references :artile

      t.timestamps
    end
    add_index :comments, :artile_id
  end
end

 

2. add index by yourself

    remove the comment model , run rails d model comment, then do it like this

 

rails g model comment content:string article_id:integer:index

 the result is the same with references