title: Rails migration error: PG::UndefinedObject: ERROR: type "number" does not exist
body: <p>I'm getting a strange Rails migration error.  I'm using the "pg" gem to interact with my Postgres database.  When I try to run a migration which adds a "number" column, I get the following error:</p>
  
  <pre><code>www-data@site:~/site/current$ RAILS_ENV=production bundle exec rake db:migrate
  == 20150115193802 AddDailyClicksToSites: migrating ============================
  -- add_column(:sites, :daily_clicks, :number)
  rake aborted!
  StandardError: An error has occurred, this and all later migrations canceled:
  
  PG::UndefinedObject: ERROR:  type "number" does not exist
  LINE 1: ALTER TABLE "sites" ADD "daily_clicks" number
  
                                             ^
  </code></pre>
  
  <p>I'm not sure why this is occurring, as previous migrations with "number" fields have worked just fine.</p>