#115 Model Caching (revised)

May 13, 2013 | 12 minutes | Performance, Active Record

Caching at a low level is a great option when the view is too dynamic to cache and you need something flexible that can work anywhere in the application. Here I show a variety of ways to use Rails.cache with Active Record.

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          rails console
        
Rails.cache.write('date', Date.today)
Rails.cache.read('date')
Rails.cache.fetch('time') { Time.now }
Rails.cache.class
article = Article.first
article.cache_key
article.touch
Rails.cache.fetch([article, "foo"]) { 123 }

          models/article.rb
        
after_commit :flush_cache

def self.cached_published
  # updated_at = published.maximum(:updated_at)
  Rails.cache.fetch([name, "published"], expires_in: 5.minutes) do
    published.to_a
  end
end

def self.cached_find(id)
  Rails.cache.fetch([name, id]) { find(id) }
end

def flush_cache
  Rails.cache.delete([self.class.name, id])
  Rails.cache.delete([self.class.name, "published"])
end

def cached_comments_count
  Rails.cache.fetch([self, "comments_count"]) { comments.size }
end

def cached_comments
  Rails.cache.fetch([self, "comments"]) { comments.to_a }
end

def cached_author
  Author.cached_find(author_id)
end

          models/comment.rb
        
belongs_to :article, touch: true

          models/author.rb
        
after_commit :flush_cache

def self.cached_find(id)
  Rails.cache.fetch([name, id], expires_in: 5.minutes) { find(id) }
end

def flush_cache
  Rails.cache.delete([self.class.name, id])
end

          articles_controller.rb
        
def index
  @articles = Article.cached_published
end

def show
  @article = Article.cached_find(params[:id])
  # ...
end

          views/articles/show.html.erb
        
<%= @article.cached_author.name %>
...
<%= pluralize(@article.cached_comments_count, "Comment") %>
...
<%= render @article.cached_comments %>