Add evilmartians/activerecord-slotted_counters gem and usage example

Gemfile

@@ -29,6 +29,8 @@ gem 'strong_migrations' # Use safe Migration patterns
 
 gem 'rubocop'
 
+gem "activerecord-slotted_counters"
+
 group :development, :test do
   gem 'active_record_doctor'
   gem 'benchmark-ips'

Gemfile.lock

@@ -73,6 +73,8 @@ GEM
       timeout (>= 0.4.0)
     activerecord-import (1.8.1)
       activerecord (>= 4.2)
+    activerecord-slotted_counters (0.3.0)
+      activerecord (>= 6.1)
     activestorage (7.2.2.1)
       actionpack (= 7.2.2.1)
       activejob (= 7.2.2.1)
@@ -358,6 +360,7 @@ PLATFORMS
 DEPENDENCIES
   active_record_doctor
   activerecord-import (~> 1.5)
+  activerecord-slotted_counters
   bcrypt (~> 3.1)
   benchmark-ips
   benchmark-memory

app/models/rider.rb

@@ -1,4 +1,7 @@
 class Rider < User
+  # https://github.com/evilmartians/activerecord-slotted_counters
+  has_slotted_counter :trip_requests
+
   has_many :trip_requests
   has_many :trips, through: :trip_requests
 end

app/models/user.rb

@@ -1,4 +1,5 @@
 class User < ApplicationRecord
+  # counter_cache trips_count
   has_secure_password
   validates :first_name, :last_name, presence: true
   validates :drivers_license_number,

db/migrate/20250617150055_create_slotted_counters.rb

@@ -0,0 +1,15 @@
+class CreateSlottedCounters < ActiveRecord::Migration[7.2]
+  def change
+    create_table :slotted_counters do |t|
+      t.string :counter_name, null: false
+      t.string :associated_record_type, null: false
+      t.integer :associated_record_id, null: false
+      t.integer :slot, null: false
+      t.integer :count, null: false
+
+      t.timestamps
+    end
+
+    add_index :slotted_counters, [:associated_record_id, :associated_record_type, :counter_name, :slot], unique: true, name: 'index_slotted_counters'
+  end
+end

db/structure.sql

@@ -27,6 +27,7 @@ DROP INDEX IF EXISTS rideshare.index_trips_on_driver_id;
 DROP INDEX IF EXISTS rideshare.index_trip_requests_on_start_location_id;
 DROP INDEX IF EXISTS rideshare.index_trip_requests_on_rider_id;
 DROP INDEX IF EXISTS rideshare.index_trip_requests_on_end_location_id;
+DROP INDEX IF EXISTS rideshare.index_slotted_counters;
 DROP INDEX IF EXISTS rideshare.index_locations_on_address;
 DROP INDEX IF EXISTS rideshare.index_fast_search_results_on_driver_id;
 ALTER TABLE IF EXISTS ONLY rideshare.vehicles DROP CONSTRAINT IF EXISTS vehicles_pkey;
@@ -35,6 +36,7 @@ ALTER TABLE IF EXISTS ONLY rideshare.users DROP CONSTRAINT IF EXISTS users_pkey;
 ALTER TABLE IF EXISTS ONLY rideshare.trips DROP CONSTRAINT IF EXISTS trips_pkey;
 ALTER TABLE IF EXISTS ONLY rideshare.trip_requests DROP CONSTRAINT IF EXISTS trip_requests_pkey;
 ALTER TABLE IF EXISTS ONLY rideshare.trip_positions DROP CONSTRAINT IF EXISTS trip_positions_pkey;
+ALTER TABLE IF EXISTS ONLY rideshare.slotted_counters DROP CONSTRAINT IF EXISTS slotted_counters_pkey;
 ALTER TABLE IF EXISTS ONLY rideshare.schema_migrations DROP CONSTRAINT IF EXISTS schema_migrations_pkey;
 ALTER TABLE IF EXISTS ONLY rideshare.vehicle_reservations DROP CONSTRAINT IF EXISTS non_overlapping_vehicle_registration;
 ALTER TABLE IF EXISTS ONLY rideshare.locations DROP CONSTRAINT IF EXISTS locations_pkey;
@@ -46,6 +48,7 @@ ALTER TABLE IF EXISTS rideshare.users ALTER COLUMN id DROP DEFAULT;
 ALTER TABLE IF EXISTS rideshare.trips ALTER COLUMN id DROP DEFAULT;
 ALTER TABLE IF EXISTS rideshare.trip_requests ALTER COLUMN id DROP DEFAULT;
 ALTER TABLE IF EXISTS rideshare.trip_positions ALTER COLUMN id DROP DEFAULT;
+ALTER TABLE IF EXISTS rideshare.slotted_counters ALTER COLUMN id DROP DEFAULT;
 ALTER TABLE IF EXISTS rideshare.locations ALTER COLUMN id DROP DEFAULT;
 DROP SEQUENCE IF EXISTS rideshare.vehicles_id_seq;
 DROP TABLE IF EXISTS rideshare.vehicles;
@@ -57,6 +60,8 @@ DROP SEQUENCE IF EXISTS rideshare.trip_requests_id_seq;
 DROP TABLE IF EXISTS rideshare.trip_requests;
 DROP SEQUENCE IF EXISTS rideshare.trip_positions_id_seq;
 DROP TABLE IF EXISTS rideshare.trip_positions;
+DROP SEQUENCE IF EXISTS rideshare.slotted_counters_id_seq;
+DROP TABLE IF EXISTS rideshare.slotted_counters;
 DROP VIEW IF EXISTS rideshare.search_results;
 DROP TABLE IF EXISTS rideshare.schema_migrations;
 DROP SEQUENCE IF EXISTS rideshare.locations_id_seq;
@@ -314,6 +319,41 @@ CREATE VIEW rideshare.search_results AS
   ORDER BY (count(t.rating)) DESC;
 
 
+--
+-- Name: slotted_counters; Type: TABLE; Schema: rideshare; Owner: -
+--
+
+CREATE TABLE rideshare.slotted_counters (
+    id bigint NOT NULL,
+    counter_name character varying NOT NULL,
+    associated_record_type character varying NOT NULL,
+    associated_record_id integer NOT NULL,
+    slot integer NOT NULL,
+    count integer NOT NULL,
+    created_at timestamp(6) without time zone NOT NULL,
+    updated_at timestamp(6) without time zone NOT NULL
+);
+
+
+--
+-- Name: slotted_counters_id_seq; Type: SEQUENCE; Schema: rideshare; Owner: -
+--
+
+CREATE SEQUENCE rideshare.slotted_counters_id_seq
+    START WITH 1
+    INCREMENT BY 1
+    NO MINVALUE
+    NO MAXVALUE
+    CACHE 1;
+
+
+--
+-- Name: slotted_counters_id_seq; Type: SEQUENCE OWNED BY; Schema: rideshare; Owner: -
+--
+
+ALTER SEQUENCE rideshare.slotted_counters_id_seq OWNED BY rideshare.slotted_counters.id;
+
+
 --
 -- Name: trip_positions; Type: TABLE; Schema: rideshare; Owner: -
 --
@@ -491,6 +531,13 @@ ALTER SEQUENCE rideshare.vehicles_id_seq OWNED BY rideshare.vehicles.id;
 ALTER TABLE ONLY rideshare.locations ALTER COLUMN id SET DEFAULT nextval('rideshare.locations_id_seq'::regclass);
 
 
+--
+-- Name: slotted_counters id; Type: DEFAULT; Schema: rideshare; Owner: -
+--
+
+ALTER TABLE ONLY rideshare.slotted_counters ALTER COLUMN id SET DEFAULT nextval('rideshare.slotted_counters_id_seq'::regclass);
+
+
 --
 -- Name: trip_positions id; Type: DEFAULT; Schema: rideshare; Owner: -
 --
@@ -573,6 +620,14 @@ ALTER TABLE ONLY rideshare.schema_migrations
     ADD CONSTRAINT schema_migrations_pkey PRIMARY KEY (version);
 
 
+--
+-- Name: slotted_counters slotted_counters_pkey; Type: CONSTRAINT; Schema: rideshare; Owner: -
+--
+
+ALTER TABLE ONLY rideshare.slotted_counters
+    ADD CONSTRAINT slotted_counters_pkey PRIMARY KEY (id);
+
+
 --
 -- Name: trip_positions trip_positions_pkey; Type: CONSTRAINT; Schema: rideshare; Owner: -
 --
@@ -635,6 +690,13 @@ CREATE UNIQUE INDEX index_fast_search_results_on_driver_id ON rideshare.fast_sea
 CREATE UNIQUE INDEX index_locations_on_address ON rideshare.locations USING btree (address);
 
 
+--
+-- Name: index_slotted_counters; Type: INDEX; Schema: rideshare; Owner: -
+--
+
+CREATE UNIQUE INDEX index_slotted_counters ON rideshare.slotted_counters USING btree (associated_record_id, associated_record_type, counter_name, slot);
+
+
 --
 -- Name: index_trip_requests_on_end_location_id; Type: INDEX; Schema: rideshare; Owner: -
 --
@@ -776,6 +838,7 @@ ALTER TABLE ONLY rideshare.trip_requests
 SET search_path TO rideshare;
 
 INSERT INTO "schema_migrations" (version) VALUES
+('20250617150055'),
 ('20231220043547'),
 ('20231218215836'),
 ('20231213045957'),

docs/slotted_counters.md

@@ -0,0 +1,26 @@
+# Slotted Counters
+
+A Rider can track its trip_requests.
+
+```rb
+# https://github.com/evilmartians/activerecord-slotted_counters
+has_slotted_counter :trip_requests
+```
+
+Increment counter manually
+```
+rideshare(dev)> Rider.increment_counter(:trip_requests_count, rider.id)
+  TRANSACTION (9.1ms)  BEGIN
+   (2.3ms)  INSERT INTO "slotted_counters" ("counter_name","associated_record_type","associated_record_id","slot","count","created_at","updated_at") VALUES ('trip_requests_count', 'Rider', 20200, 86, 1, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP) ON CONFLICT ("associated_record_id","associated_record_type","counter_name","slot") DO UPDATE SET count = slotted_counters.count + EXCLUDED.count RETURNING "id"
+  TRANSACTION (0.3ms)  COMMIT
+```
+
+Access:
+```
+rider.trip_requests_count
+```
+
+## Why the "slot"?
+By having a limit of rand(100), there are up to 100 possible records representing the total count.
+
+A slot keeps a counter, and its counter is updated on increment. This distributes the updates and avoids locking the same row.

docs/slotted_counters_bench.rb

@@ -0,0 +1,15 @@
+# Run with Rails Runner
+rider = Rider.last
+10_000.times do
+  Rider.increment_counter(:trip_requests_count, rider.id)
+end
+
+# Although there are 10,000 increments for the same
+# Rider, we don't have 10K records in slotted_counters
+# due to the "slot" distributing the inserts
+#
+# This controls the growth of slotter_counters
+# compared with a insert-per-increment approach
+
+puts "getting Rider trip_requests_count"
+puts rider.trip_requests_count