PERF: improve performance for featured user calculation

app/models/topic_featured_users.rb

@@ -24,6 +24,8 @@ class TopicFeaturedUsers
 
   def self.ensure_consistency!(topic_id=nil)
 
+    filter = "#{"AND t.id = #{topic_id.to_i}" if topic_id}"
+
     sql = <<SQL
 
 WITH cte as (
@@ -38,6 +40,7 @@ WITH cte as (
           NOT p.hidden AND
           p.user_id <> t.user_id AND
           p.user_id <> t.last_post_user_id
+          #{filter}
     GROUP BY t.id, p.user_id
 ),
 
@@ -69,7 +72,7 @@ WHERE x.id = tt.id AND
   COALESCE(featured_user2_id,-99) <> COALESCE(featured_user2,-99) OR
   COALESCE(featured_user3_id,-99) <> COALESCE(featured_user3,-99) OR
   COALESCE(featured_user4_id,-99) <> COALESCE(featured_user4,-99)
-) #{"AND x.id = #{topic_id.to_i}" if topic_id}
+)
 SQL
 
     Topic.exec_sql(sql)