custom_counter_cache
A simple approach to creating a custom counter cache that can be used across multiple models.
== Custom Counter Cache
This is a simple approach to creating a custom counter cache in Rails that can be used across multiple models.
=== Requirements
- Ruby >= 3.1
- Rails >= 7.2
=== Installation
Add the following to your Gemfile:
gem 'custom_counter_cache'
=== Example
== Class with counter cache
This is the block that will be used to calculate the value for the counter cache. It will be called by other models through their association via an after_save or after_destroy callback.
include CustomCounterCache::Model define_counter_cache :articles_count do |user| user.articles.where(state: 'published').count end
== Class with callbacks
This will define the after_create, after_update and after_destroy callbacks. An :if option can be provided to limit when these callbacks get triggered.
include CustomCounterCache::Model update_counter_cache :user, :articles_count, if: -> (article) { article.state_changed? }
These callbacks can be added to any number of models that might need to change the counter cache.
== Counter Cache
To store the counter cache you need to create a column for the model with the counter cache (example: articles_count).
If you would like to store all of your counter caches in a single table, you can use this migration:
create_table :counters do |t| t.references :countable, polymorphic: true t.string :key, null: false t.integer :value, null: false, default: 0 t.timestamps end add_index :counters, [ :countable_id, :countable_type, :key ], unique: true
Here is the example model to go with:
class Counter < ActiveRecord::Base belongs_to :countable, polymorphic: true validates :countable, presence: true end
If you would like to store your counter cache in an existing table, you can use this migration:
def change add_column :users, :articles_count, :integer, default: 0, null: false end
To backfill your counters, run something like this either in a migration or in the console:
User.select(:id).find_each(batch_size: 100) { |u| u.update_articles_count }