PERF: new table used for title similarity search

db/migrate/20140808051823_create_topic_search_index.rb

@@ -0,0 +1,17 @@
+class CreateTopicSearchIndex < ActiveRecord::Migration
+  def up
+    # used for similarity search
+    create_table :topic_search_data, id: false do |t|
+      t.integer :topic_id, null: false, primary_key: true
+      t.text :raw_data
+      t.string :locale, null: false
+      t.tsvector :search_data
+    end
+
+    execute "CREATE INDEX idx_search_topic ON topic_search_data USING gin (search_data)"
+  end
+
+  def down
+    drop_table :topic_search_data
+  end
+end