Question

我跟随low-level caching tutorial found on Heroku's website。几乎逐字复制他们的例子，这是我的方法：

Trip.test_low_level()

据我所知，这应该是：

第一次调用Trip.test_low_level()时执行查询
第二次Trip.test_low_level() Trip Load (6.2ms) SELECT "trips".* FROM "trips" INNER JOIN "destination_orders" ON "destination_orders"."trip_id" = "trips"."id" INNER JOIN "destinations" ON "destinations"."id" = "destination_orders"."destination_id" WHERE (destinations.id = 382) => #<ActiveRecord::Relation [#<Trip id: 2783, title: "Test Saving".... Trip.test_low_levle() Trip Load (3.6ms) SELECT "trips".* FROM "trips" INNER JOIN "destination_orders" ON "destination_orders"."trip_id" = "trips"."id" INNER JOIN "destinations" ON "destinations"."id" = "destination_orders"."destination_id" WHERE (destinations.id = 382) => #<ActiveRecord::Relation [#<Trip id: 2783, title: "Test Saving"，它应该查找名为＆＃39; test_destinations＆＃39;的缓存。并返回结果而不查询数据库。

但是，无论我运行该方法多少次，仍然会调用该查询。以下是我的终端的结果。

Rails.cache.fetch('test_destinations')
  Trip Load (5.0ms)  SELECT "trips".* FROM "trips" INNER JOIN "destination_orders" ON "destination_orders"."trip_id" = "trips"."id" INNER JOIN "destinations" ON "destinations"."id" = "destination_orders"."destination_id" WHERE (destinations.id = 382)
 => #<ActiveRecord::Relation [#<Trip id: 2783, title: "Test Saving"...

即使我直接调用缓存，也会得到相同的结果：

# In the development environment your application's code is reloaded on
  # every request. This slows down response time but is perfect for development
  # since you don't have to restart the web server when you make code changes.
  config.cache_classes = false

  # Do not eager load code on boot.
  config.eager_load = false

  # Show full error reports and disable caching.
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = true

如何防止它第二次访问数据库？

编辑：这是我在development.rb中的设置

# Code is not reloaded between requests.
  config.cache_classes = true

  # Eager load code on boot. This eager loads most of Rails and
  # your application in memory, allowing both threaded web servers
  # and those relying on copy on write to perform better.
  # Rake tasks automatically ignore this option for performance.
  config.eager_load = true

  # Full error reports are disabled and caching is turned on.
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true

Production.rb

webservice

Rails 4 - 低级缓存仍在查询数据库

0 个答案: