tags: automatically fix incorrect tag counts during maintenance.

* Automatically fix all tags with incorrect counts during daily
  maintenance (previously only tags with negative counts were fixed).
* Log fixed tags to NewRelic.
* Remove the ability to manually fix tag counts with the "Fix" button on
  the /tags listing. This is no longer necessary now that tags are
  fixed automatically.

app/models/tag.rb

@@ -99,24 +99,26 @@ class Tag < ApplicationRecord
         Tag.where(:name => tag_names).update_all("post_count = post_count - 1")
       end
 
-      def clean_up_negative_post_counts!
-        Tag.where("post_count < 0").find_each do |tag|
-          tag_alias = TagAlias.where("status in ('active', 'processing') and antecedent_name = ?", tag.name).first
-          tag.fix_post_count
-          if tag_alias
-            tag_alias.consequent_tag.fix_post_count
-          end
-        end
+      def regenerate_post_counts!
+        sql = <<~SQL
+          UPDATE tags
+          SET post_count = true_count
+          FROM (
+            SELECT tag, COUNT(*) AS true_count
+            FROM posts, unnest(string_to_array(tag_string, ' ')) AS tag
+            GROUP BY tag
+          ) true_counts, tags AS old_tags
+          WHERE
+            tags.name = tag
+            AND tags.post_count != true_count
+            AND old_tags.id = tags.id
+          RETURNING tags.*, old_tags.post_count AS old_post_count
+        SQL
+
+        updated_tags = Tag.find_by_sql(sql)
+        updated_tags
       end
     end
-
-    def real_post_count
-      @real_post_count ||= Post.raw_tag_match(name).where("true /* Tag#real_post_count */").count
-    end
-
-    def fix_post_count
-      update_column(:post_count, real_post_count)
-    end
   end
 
   module CategoryMethods

app/models/tag_alias.rb

@@ -145,9 +145,6 @@ class TagAlias < TagRelationship
           post.update(tag_string: fixed_tags)
         end
       end
-
-      antecedent_tag.fix_post_count if antecedent_tag
-      consequent_tag.fix_post_count if consequent_tag
     end
   end