reimplement Tag.trending to use old danbooru 1 behavior

app/models/tag.rb

@@ -121,20 +121,25 @@ class Tag < ActiveRecord::Base
       Cache.get("popular-tags", 1.hour) do
         CurrentUser.scoped(User.admins.first, "127.0.0.1") do
           n = 1
-          results = []
+          counts = {}
 
-          while results.empty? && n < 256
+          while counts.empty? && n < 256
-            query = n.days.ago.strftime("date:>%Y-%m-%d")
+            tag_strings = Post.select_values_sql("select tag_string from posts where created_at >= ? order by md5 limit 100", n.days.ago)
-            results = RelatedTagCalculator.calculate_from_sample_to_array(query)
+            tag_strings.each do |tag_string|
+              tag_string.scan(/\S+/).each do |tag|
+                counts[tag] ||= 0
+                counts[tag] += 1
+              end
+            end
             n *= 2
           end
 
-          results.map! do |tag_name, recent_count|
+          counts = counts.to_a.map do |tag_name, recent_count|
             tag = Tag.find_or_create_by_name(tag_name)
             [tag_name, recent_count.to_f / tag.post_count.to_f]
           end
 
-          results.sort_by! {|x| -x[1]}.map(&:first)
+          counts.sort_by {|x| -x[1]}.map(&:first)
         end
       end
     end

test/unit/tag_test.rb

@@ -14,6 +14,22 @@ class TagTest < ActiveSupport::TestCase
     CurrentUser.ip_addr = nil
   end
 
+  context ".trending" do
+    setup do
+      Timecop.travel(1.week.ago) do
+        Post.create(:tag_string => "aaa")
+        Post.create(:tag_string => "bbb")
+      end
+
+      Post.create(:tag_string => "bbb")
+      Post.create(:tag_string => "ccc")
+    end
+
+    should "order the results by the total post count" do
+      assert_equal([], Tag.trending)
+    end
+  end
+
   context "A tag category fetcher" do
     setup do
       MEMCACHE.flush_all