Fix #3934: Post#fast_count has very slow worst case behavior.

app/models/post.rb

@@ -1207,10 +1207,6 @@ class Post < ApplicationRecord
         PostReadOnly.tag_match(tags).count
       end
 
-      if count.nil?
-        count = fast_count_search_batched(tags, options)
-      end
-
       if count.nil?
         # give up
         if options[:raise_on_timeout]
@@ -1227,26 +1223,6 @@ class Post < ApplicationRecord
       return nil
     end
 
-    def fast_count_search_batched(tags, options)
-      # this is slower but less likely to timeout
-      i = Post.maximum(:id)
-      sum = 0
-      while i > 0
-        count = PostReadOnly.with_timeout(1_000, nil, {:tags => tags}) do
-          sum += PostReadOnly.tag_match(tags).where("id <= ? and id > ?", i, i - 25_000).count
-          i -= 25_000
-        end
-
-        if count.nil?
-          return nil
-        end
-      end
-      sum
-
-    rescue PG::ConnectionBad
-      return nil
-    end
-
     def fix_post_counts(post)
       post.set_tag_counts(false)
       if post.changes_saved?