我看到.where语句用很多CACHE User Load消息做了很多请求，而不是关联。这是真的还是假的？
在本例中，我得到一个ActiveRecord_Relation：
@dogs = Dog.where(user_id: current_user.id).order('created_at DESC')在另一种情况下，我得到一个ActiveRecord_Associations_CollectionProxy：
@dogs = current_user.dogs.order('created_at DESC')当我在视图中迭代时
<% @dogs.each do |dog| %>
<div><%= dog.name %></div>
<% end %>我在控制台日志中收到不同的消息：
ActiveRecord_Relation：
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
CACHE User Load (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]ActiveRecord_Associations_CollectionProxy：
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 15], ["LIMIT", 1]]
Dog Load (0.6ms) SELECT "dogs".* FROM "dogs" WHERE "dogs"."user_id" = ? ORDER BY "dogs"."created_at" DESC [["user_id", 15]]哪种方式更好？非常感谢。
1条答案
按热度按时间lpwwtiir1#
看起来在这两种情况下
current_user都应该只被调用一次。假设current_user方法有这样的实现：我不清楚为什么
User.find_by会在“ActiveRecord_Relation”版本中被调用多次，但这似乎一定是发生了什么。Rails会缓存这个查询的结果，所以每次在你第一次命中一个热缓存后。要排除这种情况，可以使用memoize
#current_user。这应该可以防止Active Record在第一次调用current_user之后每次都看到查询。