new_connection

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 675
        def new_connection
          connection = Base.public_send(db_config.adapter_method, db_config.configuration_hash)
          connection.pool = self
          connection.check_version
          connection
        rescue ConnectionNotEstablished => ex
          raise ex.set_pool(self)
        end