added constraint for fav search

app/models/favorite.rb

@@ -1,4 +1,4 @@
 class Favorite < ActiveRecord::Base
   belongs_to :post
-  scope :for_user, lambda {|user_id| where("user_id = #{user_id}")}
+  scope :for_user, lambda {|user_id| where("user_id % 100 = #{user_id.to_i % 100} and user_id = #{user_id.to_i}")}
 end