Ruby on Rails: How to set up "find" options in order to not use cache

In Ruby on Rails you can find records from the database with this syntax:

<model_name>.find_by_<field_name>()

Examples: User.find_by_email('test@test.test'), User.find_by_id(1), ...

Time ago, if I am not wrong, I read somewhere that 开发者_如何学JAVAyou can explicitly disable caching for 'find' operations, but I can not remember how.

Can someone help me remember?

You can use ActiveRecord::QueryCache.uncached like this:

User.find_by_email('test@test.test')
User.find_by_email('test@test.test') # Will return cached result

User.uncached do
  User.find_by_email('test@test.test')
  User.find_by_email('test@test.test') # Will query the database again
end

In a controller, it would look something like this:

def show # users#index action
  User.uncached do
    @user = User.find_by_email('test@test.test')
    @another_user = User.find_by_email('test@test.test') # Will query database        
  end

  User.find_by_email('test@test.test') # Will *not* query database, as we're outside of the Users.uncached block
end          

Obviously, in a model, you just have to do:

class User < ActiveRecord::Base
  def self.do_something
    uncached do
      self.find_by_email('test@test.test')
      self.find_by_email('test@test.test') # Will query database
    end
  end
end

User.do_something # Will run both queries

(Note: assuming Rails3, since Rails2 doesn't have default caching.)

This should work as you want it to out of the box:

1. Queries caches are destroyed after each action ( http://guides.rubyonrails.org/caching_with_rails.html paragraph 1.5)
2. In addition, it seems (http://ryandaigle.com/articles/2007/2/7/what-s-new-in-edge-rails-activerecord-explicit-caching) that caches are also destroyed on attribute/record updates

Do you have a specific use case not covered by the default configuration?