def call(env)
  connection    = ActiveRecord::Base.connection
  enabled       = connection.query_cache_enabled
  connection_id = ActiveRecord::Base.connection_id
  connection.enable_query_cache!
  response = @app.call(env)
  response[2] = Rack::BodyProxy.new(response[2]) do
    restore_query_cache_settings(connection_id, enabled)
  end
  response
rescue Exception => e
  restore_query_cache_settings(connection_id, enabled)
  raise e
end

def initialize(app)
  @app = app
end

def restore_query_cache_settings(connection_id, enabled)
  ActiveRecord::Base.connection_id = connection_id
  ActiveRecord::Base.connection.clear_query_cache
  ActiveRecord::Base.connection.disable_query_cache! unless enabled
end