Question

Is there a way to do this in Rails:
I have an activerecord query

@posts = Post.find_by_id(10)

Anytime the query is called, SQL is generated and executed at the DB that looks like this

SELECT * FROM 'posts' WHERE id = 10

This happens every time the AR query is executed. Similarly with a helper method like this

<%= f.textarea :name => 'foo' %> 
#=> <input type='textarea' name='foo' />

I write some Railsy code that generates some text that is used by some other system (database, web browser). I’m wondering if there’s a way to write an AR query or a helper method call that generates the text in the file. This way the text rendering is only done once (each time the code changes) instead of each time the method is called?

Answer 1

Like Radar suggested you should probably look into Rails caching. You can start with something simple like the memory store or file cache and then move to something better like memcached if necessary. You can throw in some caching into the helper method which will cache the result after it is queried once. So for example you can do:

    id = 10 # id is probably coming in as a param/argument
    cache_key = "Post/#{id}"
    @post = Rails.cache.read(cache_key)
    if @post.nil?
      @post = Post.find_by_id(id)
      # Write back to the cache for the next time
      Rails.cache.write(cache_key,@post)
    end

The only other thing left to do is put in some code to expire the cache entry if the post changes. For that take a look at using “Sweepers” in Rails. Alternatively you can look at some of the caching gems like Cache-fu and Cached-model.