extension_enabled?

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 349
      def extension_enabled?(name)
        if supports_extensions?
          res = exec_query "SELECT EXISTS(SELECT * FROM pg_available_extensions WHERE name = '#{name}' AND installed_version IS NOT NULL) as enabled",
            'SCHEMA'
          res.cast_values.first
        end
      end