class ActiveRecord::ConnectionAdapters::ConnectionHandler

def resolve_pool_config(config, owner_name, role, shard)
  db_config = Base.configurations.resolve(config)
  raise(AdapterNotSpecified, "database configuration does not specify adapter") unless db_config.adapter
  # Require the adapter itself and give useful feedback about
  #   1. Missing adapter gems and
  #   2. Adapter gems' missing dependencies.
  path_to_adapter = "active_record/connection_adapters/#{db_config.adapter}_adapter"
  begin
    require path_to_adapter
  rescue LoadError => e
    # We couldn't require the adapter itself. Raise an exception that
    # points out config typos and missing gems.
    if e.path == path_to_adapter
      # We can assume that a non-builtin adapter was specified, so it's
      # either misspelled or missing from Gemfile.
      raise LoadError, "Could not load the '#{db_config.adapter}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
      # Bubbled up from the adapter require. Prefix the exception message
      # with some guidance about how to address it and reraise.
    else
      raise LoadError, "Error loading the '#{db_config.adapter}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
    end
  end
  unless ActiveRecord::Base.respond_to?(db_config.adapter_method)
    raise AdapterNotFound, "database configuration specifies nonexistent #{db_config.adapter} adapter"
  end
  ConnectionAdapters::PoolConfig.new(owner_name, db_config, role, shard)
end