title: change column type to integer rails
body: <p>I have run a migration when trying  to change on heroku table column from string to integer:
  This is my migration:</p>
  
  <pre><code>class ChangePriceTypeInItems &lt; ActiveRecord::Migration
    def change
      change_column :items, :price, :integer
    end
  end
  </code></pre>
  
  <p>And this is my error:
  What do I do?</p>
  
  <pre><code>ActiveRecord::StatementInvalid: PG::Error: ERROR:  column "price" cannot be cast automatically to type integer
  HINT:  You might need to specify "USING price::integer".
  : ALTER TABLE "items" ALTER COLUMN "price" TYPE integer
  </code></pre>