Make account search blazing fast and rank followers/followees higher in the results

db/migrate/20170317193015_add_search_index_to_accounts.rb

@@ -0,0 +1,9 @@
+class AddSearchIndexToAccounts < ActiveRecord::Migration[5.0]
+  def up
+    execute 'CREATE INDEX search_index ON accounts USING gin((setweight(to_tsvector(\'simple\', accounts.display_name), \'A\') || setweight(to_tsvector(\'simple\', accounts.username), \'B\') || setweight(to_tsvector(\'simple\', coalesce(accounts.domain, \'\')), \'C\')));'
+  end
+
+  def down
+    remove_index :accounts, name: :search_index
+  end
+end