PERF: Active Record #pluck is twice faster

PERF: SqlBuilder bypasses AR converters and uses PG directly

lib/topic_query.rb

@@ -137,7 +137,6 @@ class TopicQuery
     pinned_ids = query.where('pinned_at IS NOT NULL AND category_id = ?', category.id)
                       .order('pinned_at DESC').pluck(:id)
     non_pinned_ids = query.where('pinned_at IS NULL OR category_id <> ?', category.id).pluck(:id)
-
     (pinned_ids + non_pinned_ids)[0...@options[:per_page]]
   end