title: Rails database model not updating
body: <p>I am creating a database model for an optimisation machine called the SimutronX. I have just change the variable name of one of the database keys and added an index. </p>
  
  <p>Current migration file:</p>
  
  <pre><code>class CreateSimutronXes &lt; ActiveRecord::Migration[5.0]
    def change
      create_table :simutron_xes do |t|
        t.integer :num_constraints
        t.integer :num_coefficients
        t.boolean :max
        t.decimal :obj_func
  
        t.timestamps
      end
      add_index :simutron_xes, [:user_id, :created_at]
    end
  end
  </code></pre>
  
  <p>Old migration file:</p>
  
  <pre><code>class CreateSimutronXes &lt; ActiveRecord::Migration[5.0]
    def change
      create_table :simutron_xes do |t|
        t.integer :num_constraints
        t.integer :num_coefficients
        t.boolean :min_max
        t.decimal :obj_func
  
        t.timestamps
      end
    end
  end
  </code></pre>
  
  <p>I have saved the new file and run a <code>rails db:migrate</code> which has completed successfully. After I ran the migration I dropped into the rails console sandbox to test the model.</p>
  
  <pre><code>brotherlongtail:~/workspace/Simutronix (master) $ rails console --sandbox
  Running via Spring preloader in process 8135
  Loading development environment in sandbox (Rails 5.0.2)
  Any modifications you make will be rolled back on exit
  &gt;&gt; SimutronX.new
  =&gt; #&lt;SimutronX id: nil, constraint: nil, coefficient: nil, min_max: nil, obj_func: nil, created_at: nil, updated_at: nil&gt;
  </code></pre>
  
  <p>The model doesn't seem to have updated. What are the additional steps required to get the model to properly update?</p>