Question

I’m totaling the rows in one of my models using Model.count and am a bit concerned about performance, as eventually, this model will get very large, and, therefore, SELECT COUNT (*) very slow.

Is there a way to use counter_cache without the :belongs_to relationship? Or another performance-friendly way of counting the rows? I thought about making another model, just one where I store calculations like this but not sure that’s the best way.

Answer 1

Even more trivial than making a Cache model is to just use Rails.cache.

Rails.cache.read("elephant_count") #=> nil
Rails.cache.write("elephant_count", 1) #=> true
Rails.cache.read("elephant_count") #=> 1

Rails uses a file store by default (tmp/cache).

Then you could just place a Rails.cache.write increment and decrement into your model’s after_create and after_destroy hooks, and override Model.size with a call to Rails.cache.read.

You could initialize the cache whenever Rails first initializes by placing a file named something like initialize_cache.rb in config/initializers containing:

Rails.cache.write('elephant_count', 0) if Rails.cache.read('elephant_count').nil?