How to cache a query in Ruby on Rails 3

Question

I have the following query in my application

@categories = Category.joins(:posts).select(\'distinct categories.*\').order(\'label\')

This query

Answer 1

In your controller, you can try something like:

@categories = Rails.cache.fetch('categories', :expires_in => 24.hours) { Category.joins(:posts).select('distinct categories.*').order('label') }

Which will only read to see if the following data block 'categories' has been cached and not expired. If expired after 24 hours, will then query the model and write the new record into Rails cache.

For more information, I followed the following guide.

Try it out. I have it working this way. Hope that helps.

Answer 2

You can use fragment caching for the part of your view template that displays the categories. This means that the categories will be served from the cache store and the query will only be executed once until the cache is expired (by using the expire_fragment method).

• Fragment Caching Rails Guide