# File lib/active_record/connection_adapters/abstract/connection_specification.rb, line 128
    def self.establish_connection(spec = ENV["DATABASE_URL"])
      resolver = ConnectionSpecification::Resolver.new spec, configurations
      spec = resolver.spec

      unless respond_to?(spec.adapter_method)
        raise AdapterNotFound, "database configuration specifies nonexistent #{spec.config[:adapter]} adapter"
      end

      remove_connection
      connection_handler.establish_connection name, spec
    end