Introduce InstanceStatistics::Measurement model

This change introduces InstanceStatistics::Measurement model. Note
that this change is not user facing.

app/models/analytics/instance_statistics.rb

+# frozen_string_literal: true
+
+module Analytics
+  module InstanceStatistics
+    def self.table_name_prefix
+      'analytics_instance_statistics_'
+    end
+  end
+end

app/models/analytics/instance_statistics/measurement.rb

+# frozen_string_literal: true
+
+module Analytics
+  module InstanceStatistics
+    class Measurement < ApplicationRecord
+      enum identifier: { projects: 1, users: 2 }
+
+      validates :recorded_at, :identifier, :count, presence: true
+      validates :recorded_at, uniqueness: { scope: :identifier }
+    end
+  end
+end

changelogs/unreleased/241673-model-for-storing-instance-level-statistics.yml

+---
+title: Create table for storing Instance Statistics object counts
+merge_request: 40605
+author:
+type: added

db/fixtures/development/29_instance_statistics.rb

+# frozen_string_literal: true
+
+require './spec/support/sidekiq_middleware'
+
+Gitlab::Seeder.quiet do
+  model_class = Analytics::InstanceStatistics::Measurement
+  recorded_at = Date.today
+
+  # Insert random counts for the last 10 weeks
+  measurements = 10.times.flat_map do
+    recorded_at = (recorded_at - 1.week).end_of_week.end_of_day - 5.minutes
+
+    model_class.identifiers.map do |_, id|
+      {
+        recorded_at: recorded_at,
+        count: rand(1_000_000),
+        identifier: id
+      }
+    end
+  end
+
+  model_class.upsert_all(measurements, unique_by: [:identifier, :recorded_at])
+
+  print '.'
+end

db/migrate/20200827114902_create_analytics_instance_statistics_measurements.rb

+# frozen_string_literal: true
+
+class CreateAnalyticsInstanceStatisticsMeasurements < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+  UNIQUE_INDEX_NAME = 'index_on_instance_statistics_recorded_at_and_identifier'
+
+  def change
+    create_table :analytics_instance_statistics_measurements do |t|
+      t.bigint :count, null: false
+      t.datetime_with_timezone :recorded_at, null: false
+      t.integer :identifier, limit: 2, null: false
+    end
+
+    add_index :analytics_instance_statistics_measurements, [:identifier, :recorded_at], unique: true, name: UNIQUE_INDEX_NAME
+  end
+end

db/schema_migrations/20200827114902

+f581bd5f5ec26dc33643c77fb8c7a64a9053b55c3f6a7281fea89ac4790a58d2
\ No newline at end of file

db/structure.sql

@@ -8930,6 +8930,22 @@ CREATE SEQUENCE public.analytics_cycle_analytics_project_stages_id_seq
 
 ALTER SEQUENCE public.analytics_cycle_analytics_project_stages_id_seq OWNED BY public.analytics_cycle_analytics_project_stages.id;
 
+CREATE TABLE public.analytics_instance_statistics_measurements (
+    id bigint NOT NULL,
+    count bigint NOT NULL,
+    recorded_at timestamp with time zone NOT NULL,
+    identifier smallint NOT NULL
+);
+
+CREATE SEQUENCE public.analytics_instance_statistics_measurements_id_seq
+    START WITH 1
+    INCREMENT BY 1
+    NO MINVALUE
+    NO MAXVALUE
+    CACHE 1;
+
+ALTER SEQUENCE public.analytics_instance_statistics_measurements_id_seq OWNED BY public.analytics_instance_statistics_measurements.id;
+
 CREATE TABLE public.analytics_language_trend_repository_languages (
     file_count integer DEFAULT 0 NOT NULL,
     programming_language_id bigint NOT NULL,
@@ -16814,6 +16830,8 @@ ALTER TABLE ONLY public.analytics_cycle_analytics_group_value_streams ALTER COLU
 
 ALTER TABLE ONLY public.analytics_cycle_analytics_project_stages ALTER COLUMN id SET DEFAULT nextval('public.analytics_cycle_analytics_project_stages_id_seq'::regclass);
 
+ALTER TABLE ONLY public.analytics_instance_statistics_measurements ALTER COLUMN id SET DEFAULT nextval('public.analytics_instance_statistics_measurements_id_seq'::regclass);
+
 ALTER TABLE ONLY public.appearances ALTER COLUMN id SET DEFAULT nextval('public.appearances_id_seq'::regclass);
 
 ALTER TABLE ONLY public.application_setting_terms ALTER COLUMN id SET DEFAULT nextval('public.application_setting_terms_id_seq'::regclass);
@@ -17712,6 +17730,9 @@ ALTER TABLE ONLY public.analytics_cycle_analytics_group_value_streams
 ALTER TABLE ONLY public.analytics_cycle_analytics_project_stages
     ADD CONSTRAINT analytics_cycle_analytics_project_stages_pkey PRIMARY KEY (id);
 
+ALTER TABLE ONLY public.analytics_instance_statistics_measurements
+    ADD CONSTRAINT analytics_instance_statistics_measurements_pkey PRIMARY KEY (id);
+
 ALTER TABLE ONLY public.appearances
     ADD CONSTRAINT appearances_pkey PRIMARY KEY (id);
 
@@ -20325,6 +20346,8 @@ CREATE INDEX index_on_id_partial_with_legacy_storage ON public.projects USING bt
 
 CREATE INDEX index_on_identities_lower_extern_uid_and_provider ON public.identities USING btree (lower((extern_uid)::text), provider);
 
+CREATE UNIQUE INDEX index_on_instance_statistics_recorded_at_and_identifier ON public.analytics_instance_statistics_measurements USING btree (identifier, recorded_at);
+
 CREATE INDEX index_on_users_name_lower ON public.users USING btree (lower((name)::text));
 
 CREATE INDEX index_open_project_tracker_data_on_service_id ON public.open_project_tracker_data USING btree (service_id);

spec/factories/instance_statistics/measurement.rb

+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :instance_statistics_measurement, class: 'Analytics::InstanceStatistics::Measurement' do
+    recorded_at { Time.now }
+    identifier { Analytics::InstanceStatistics::Measurement.identifiers[:projects] }
+    count { 1_000 }
+  end
+end

spec/models/analytics/instance_statistics/measurement_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Analytics::InstanceStatistics::Measurement, type: :model do
+  describe 'validation' do
+    let!(:measurement) { create(:instance_statistics_measurement) }
+
+    it { is_expected.to validate_presence_of(:recorded_at) }
+    it { is_expected.to validate_presence_of(:identifier) }
+    it { is_expected.to validate_presence_of(:count) }
+    it { is_expected.to validate_uniqueness_of(:recorded_at).scoped_to(:identifier) }
+  end
+end