Expire the stats cache an hour after generating it

When we first started caching the stats, generating them was a process
that took several minutes, so we never expired the cache.

However, there have been cases where we run into issues where the stats
shown on the screen were outdated. That's why we introduced a task to
manually expire the cache.

But now, generating the stats only takes a few seconds, so we can
automatically expire them every hour, remove all the logic needed to
manually expire them, and get rid of most of the issues related to the
cache being outdated.

app/models/budget.rb

@@ -1,7 +1,6 @@
 class Budget < ApplicationRecord
   include Measurable
   include Sluggable
-  include StatsVersionable
   include Reportable
   include Imageable
 

app/models/budget/stats.rb

@@ -181,6 +181,6 @@ def supports(supportable)
     stats_cache(*stats_methods)
 
     def full_cache_key_for(key)
-      "budgets_stats/#{budget.id}/#{phases.join}/#{key}/#{version}"
+      "budgets_stats/#{budget.id}/#{phases.join}/#{key}"
     end
 end

app/models/concerns/statisticable.rb

@@ -145,10 +145,6 @@ def calculate_percentage(fraction, total)
     (fraction * 100.0 / total).round(3)
   end
 
-  def version
-    "v#{resource.find_or_create_stats_version.updated_at.to_i}"
-  end
-
   def advanced?
     resource.advanced_stats_enabled?
   end
@@ -227,6 +223,6 @@ def range_description(start, finish)
     end
 
     def stats_cache(key, &)
-      Rails.cache.fetch(full_cache_key_for(key), &)
+      Rails.cache.fetch(full_cache_key_for(key), expires_in: 1.hour, &)
     end
 end

app/models/poll.rb

@@ -7,7 +7,6 @@ class Poll < ApplicationRecord
   include Notifiable
   include Searchable
   include Sluggable
-  include StatsVersionable
   include Reportable
   include SDG::Relatable
 

app/models/poll/stats.rb

@@ -118,6 +118,6 @@ def total_unregistered_booth
     stats_cache(*stats_methods)
 
     def full_cache_key_for(key)
-      "polls_stats/#{poll.id}/#{key}/#{version}"
+      "polls_stats/#{poll.id}/#{key}"
     end
 end

db/migrate/20240408154814_drop_stats_versions.rb

@@ -0,0 +1,8 @@
+class DropStatsVersions < ActiveRecord::Migration[6.1]
+  def change
+    drop_table :stats_versions do |t|
+      t.references :process, polymorphic: true, index: true
+      t.timestamps null: false
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2024_03_22_223950) do
+ActiveRecord::Schema[7.0].define(version: 2024_04_08_154814) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
   enable_extension "plpgsql"
@@ -1516,14 +1516,6 @@
     t.string "locale"
   end
 
-  create_table "stats_versions", id: :serial, force: :cascade do |t|
-    t.string "process_type"
-    t.integer "process_id"
-    t.datetime "created_at", precision: nil, null: false
-    t.datetime "updated_at", precision: nil, null: false
-    t.index ["process_type", "process_id"], name: "index_stats_versions_on_process_type_and_process_id"
-  end
-
   create_table "taggings", id: :serial, force: :cascade do |t|
     t.integer "tag_id"
     t.string "taggable_type"

spec/models/poll/stats_spec.rb

@@ -259,32 +259,4 @@
       end
     end
   end
-
-  describe "#version", :with_frozen_time do
-    context "record with no stats" do
-      it "returns a string based on the current time" do
-        expect(stats.version).to eq "v#{Time.current.to_i}"
-      end
-
-      it "doesn't overwrite the timestamp when called multiple times" do
-        time = Time.current
-
-        expect(stats.version).to eq "v#{time.to_i}"
-
-        unfreeze_time
-
-        travel_to 2.seconds.from_now do
-          expect(stats.version).to eq "v#{time.to_i}"
-        end
-      end
-    end
-
-    context "record with stats" do
-      before { poll.create_stats_version(updated_at: 1.day.ago) }
-
-      it "returns the version of the existing stats" do
-        expect(stats.version).to eq "v#{1.day.ago.to_i}"
-      end
-    end
-  end
 end