Forget about postgres for now, depend on On duplicate key update

app/models/services/facebook.rb

@@ -42,7 +42,6 @@ class Services::Facebook < Service
     url = "https://graph.facebook.com/me/friends?fields[]=name&fields[]=picture&access_token=#{URI.escape(self.access_token)}"
     response = Faraday.get(url)
     data = JSON.parse(response.body)['data']
-    ServiceUser.where(:service_id => self.id).delete_all
     s_users = data.map{ |p|
       ServiceUser.new(:service_id => self.id, :uid => p["id"], :photo_url => p["picture"], :name => p["name"])
     }