Active Record slotted counters
This gem adds slotted counters support to Active Record counter cache. Slotted counters help to reduce contention on a single row update in case you have many concurrent operations (like updating a page views counter during traffic spikes).
Read more about slotted counters in this post.
Add to your project:
# Gemfile gem "activerecord-slotted_counters"
Supported Ruby versions
- Ruby (MRI) >= 2.7.0
First, add and apply the required migration(-s):
bin/rails generate slotted_counters:install bin/rails db:migrate
Then, add the following line to the model to add a slotted counter:
class User < ApplicationRecord has_slotted_counter :comments end
Now you can use all the common counter cache APIs as before:
# Manipulating the counter explicitly user = User.first User.increment_counter(:comments_count, user.id) User.decrement_counter(:comments_count, user.id) User.reset_counters(user.id, :comments) # etc. # Reading the value user.comments_count
Under the hood, a row in the
slotted_counters table is created associated with the record.
NOTE: Reading the current value performs SQL query once:
user.comments_count #=> select * from slotted_counters where ... user.comments_count #=> no sql
If you want to preload counters for multiple records, you can use a convenient
User.all.with_slotted_counters(:comments).find_each do _1.comments_count #=> no sql end
counter_cache: true on
belongs_to associations also works as expected.
Limitations / TODO
- Gem supports only PostgreSQL for Rails 6
Bug reports and pull requests are welcome on GitHub at https://github.com/evilmartians/activerecord-slotted_counters.
This gem is generated via new-gem-generator.
The gem is available as open source under the terms of the MIT License.