consolidate sql fragment to cast story/comment score

app/indices/comment_index.rb

@@ -3,9 +3,7 @@ ThinkingSphinx::Index.define :comment, :with => :active_record do
   indexes short_id
   indexes user.username, :as => :author
 
-  has "(CAST(upvotes as #{Story.votes_cast_type}) - " <<
-    "CAST(downvotes as #{Story.votes_cast_type}))", :as => :score,
-    :type => :bigint, :sortable => true
+  has Comment.score_sql, :as => :score, :type => :bigint, :sortable => true
 
   has is_deleted
   has created_at

app/indices/story_index.rb

@@ -9,9 +9,7 @@ ThinkingSphinx::Index.define :story, :with => :active_record do
 
   has created_at, :sortable => true
   has hotness, is_expired
-  has "(CAST(upvotes as #{Story.votes_cast_type}) - " <<
-    "CAST(downvotes as #{Story.votes_cast_type}))", :as => :score,
-    :type => :bigint, :sortable => true
+  has Story.score_sql, :as => :score, :type => :bigint, :sortable => true
 
   set_property :field_weights => {
     :upvotes => 15,

app/models/comment.rb

@@ -103,6 +103,11 @@ class Comment < ActiveRecord::Base
     nil
   end
 
+  def self.score_sql
+    "(CAST(upvotes AS #{Story.votes_cast_type}) - " <<
+      "CAST(downvotes AS #{Story.votes_cast_type}))"
+  end
+
   def as_json(options = {})
     h = super(:only => [
       :short_id,

app/models/story.rb

@@ -102,6 +102,11 @@ class Story < ActiveRecord::Base
     true
   end
 
+  def self.score_sql
+    "(CAST(upvotes AS #{votes_cast_type}) - " <<
+      "CAST(downvotes AS #{votes_cast_type}))"
+  end
+
   def self.votes_cast_type
     Story.connection.adapter_name.match(/mysql/i) ? "signed" : "integer"
   end

app/models/story_repository.rb

@@ -86,8 +86,7 @@ class StoryRepository
   def top(length)
     top = base_scope.where("created_at >= (NOW() - INTERVAL " <<
       "#{length[:dur]} #{length[:intv].upcase})")
-    top.order("(CAST(upvotes AS #{Story.votes_cast_type}) - " <<
-      "CAST(downvotes AS #{Story.votes_cast_type})) DESC")
+    top.order("#{Story.score_sql} DESC")
   end
 
 private
@@ -124,8 +123,7 @@ private
   end
 
   def positive_ranked(scope)
-    scope.where("(CAST(upvotes AS #{Story.votes_cast_type}) - " <<
-      "CAST(downvotes AS #{Story.votes_cast_type})) >= -1")
+    scope.where("#{Story.score_sql} >= -1")
   end
 
   def filter_tags(scope, tags)