stopgap measure for #1210

app/models/post.rb

@@ -526,12 +526,25 @@ class Post < ActiveRecord::Base
   end
 
   module FavoriteMethods
+    def clean_fav_string?
+      rand(100) < [Math.log(fav_string.size, 2), 5].min
+    end
+
+    def clean_fav_string!
+      array = fav_string.scan(/\S+/).uniq
+      self.fav_string = array.join(" ")
+      self.fav_count = array.size
+      update_column(:fav_string, fav_string)
+      update_column(:fav_count, fav_count)
+    end
+
     def favorited_by?(user_id)
       fav_string =~ /(?:\A| )fav:#{user_id}(?:\Z| )/
     end
 
     def append_user_to_fav_string(user_id)
       update_column(:fav_string, (fav_string + " fav:#{user_id}").strip)
+      clean_fav_string! if clean_fav_string?
     end
 
     def add_favorite!(user)

app/models/user.rb

@@ -204,8 +204,17 @@ class User < ActiveRecord::Base
       Favorite.where("user_id % 100 = #{id % 100} and user_id = #{id}").order("id desc")
     end
 
+    def clean_favorite_count?
+      favorite_count < 0 || rand(100) < [Math.log(favorite_count, 2), 5].min
+    end
+
+    def clean_favorite_count!
+      update_column(:favorite_count, Favorite.for_user(id).count)
+    end
+
     def add_favorite!(post)
       Favorite.add(post, self)
+      clean_favorite_count! if clean_favorite_count?
     end
 
     def remove_favorite!(post)

db/structure.sql

@@ -2058,7 +2058,8 @@ CREATE TABLE pool_versions (
     updater_id integer NOT NULL,
     updater_ip_addr inet NOT NULL,
     created_at timestamp without time zone NOT NULL,
-    updated_at timestamp without time zone NOT NULL
+    updated_at timestamp without time zone NOT NULL,
+    name character varying(255)
 );
 
 
@@ -6410,3 +6411,5 @@ INSERT INTO schema_migrations (version) VALUES ('20130401013601');
 INSERT INTO schema_migrations (version) VALUES ('20130409191950');
 
 INSERT INTO schema_migrations (version) VALUES ('20130417221643');
+
+INSERT INTO schema_migrations (version) VALUES ('20130424121410');

test/unit/post_test.rb

@@ -741,6 +741,15 @@ class PostTest < ActiveSupport::TestCase
         CurrentUser.ip_addr = nil
       end
 
+      should "periodically clean the fav_string" do
+        @post.update_column(:fav_string, "fav:1 fav:1 fav:1")
+        @post.update_column(:fav_count, 3)
+        @post.stubs(:clean_fav_string?).returns(true)
+        @post.append_user_to_fav_string(2)
+        assert_equal("fav:1 fav:2", @post.fav_string)
+        assert_equal(2, @post.fav_count)
+      end
+
       should "increment the user's favorite_count" do
         assert_difference("CurrentUser.favorite_count", 1) do
           @post.add_favorite!(@user)

test/unit/user_test.rb

@@ -14,6 +14,19 @@ class UserTest < ActiveSupport::TestCase
       CurrentUser.ip_addr = nil
     end
 
+    context "favoriting a post" do
+      setup do
+        @user.update_column(:favorite_count, 999)
+        @user.stubs(:clean_favorite_count?).returns(true)
+        @post = FactoryGirl.create(:post)
+      end
+
+      should "periodically clean the favorite_count" do
+        @user.add_favorite!(@post)
+        assert_equal(1, @user.favorite_count)
+      end
+    end
+
     context "that has been invited by a mod" do
       setup do
         @mod = FactoryGirl.create(:moderator_user)