optimize mini leaderboards

app/jobs/warm_mini_leaderboard_cache_job.rb

@@ -0,0 +1,20 @@
+class WarmMiniLeaderboardCacheJob < ApplicationJob
+  queue_as :default
+
+  def perform
+    offsets = [ -8, -7, -6, -5, -4, -3, 0, 1, 2, 8, 9, 10, 11, 12 ]
+
+    offsets.each do |offset|
+      begin
+        LeaderboardGenerator.generate_timezone_offset_leaderboard(
+          Date.current,
+          offset,
+          :daily
+        )
+        Rails.logger.info "Warmed mini leaderboard cache for UTC#{offset >= 0 ? '+' : ''}#{offset}"
+      rescue => e
+        Rails.logger.error "Failed to warm cache for UTC#{offset >= 0 ? '+' : ''}#{offset}: #{e.message}"
+      end
+    end
+  end
+end

app/models/concerns/heartbeatable.rb

@@ -98,9 +98,19 @@ module Heartbeatable
     end
 
     def daily_streaks_for_users(user_ids, start_date: 31.days.ago)
-      # First get the raw durations using window function
+      return {} if user_ids.empty?
+      start_date = [ start_date, 30.days.ago ].max
+      keys = user_ids.map { |id| "user_streak_#{id}" }
+      streak_cache = Rails.cache.read_multi(*keys)
+
+      uncached_users = user_ids.select { |id| streak_cache["user_streak_#{id}"].nil? }
+
+      if uncached_users.empty?
+        return user_ids.index_with { |id| streak_cache["user_streak_#{id}"] || 0 }
+      end
+
       raw_durations = joins(:user)
-        .where(user_id: user_ids)
+        .where(user_id: uncached_users)
         .coding_only
         .with_valid_timestamps
         .where(time: start_date..Time.current)
@@ -128,8 +138,7 @@ module Heartbeatable
          }
        end
 
-      # Initialize the result hash with zeros for all users
-      result = user_ids.index_with { 0 }
+      result = user_ids.index_with { |id| streak_cache["user_streak_#{id}"] || 0 }
 
       # Then calculate streaks for each user
       daily_durations.each do |user_id, data|
@@ -158,6 +167,9 @@ module Heartbeatable
         end
 
         result[user_id] = streak
+
+        # Cache the streak for 1 hour
+        Rails.cache.write("user_streak_#{user_id}", streak, expires_in: 1.hour)
       end
 
       result

app/services/leaderboard_generator.rb

@@ -11,14 +11,24 @@ class LeaderboardGenerator
 
   def generate_timezone_offset_leaderboard(date, utc_offset, period_type = :daily)
     date = Date.current if date.blank?
-    users = User.users_in_timezone_offset(utc_offset).not_convicted
-    generate_leaderboard_for_users(users, date, "UTC#{utc_offset >= 0 ? '+' : ''}#{utc_offset}", period_type)
+
+    cache_key = "timezone_leaderboard_#{utc_offset}_#{date}_#{period_type}"
+
+    Rails.cache.fetch(cache_key, expires_in: 5.minutes) do
+      users = User.users_in_timezone_offset(utc_offset).not_convicted
+      generate_leaderboard_for_users(users, date, "UTC#{utc_offset >= 0 ? '+' : ''}#{utc_offset}", period_type)
+    end
   end
 
   def generate_timezone_leaderboard(date, timezone, period_type = :daily)
     date = Date.current if date.blank?
-    users = User.users_in_timezone(timezone).not_convicted
-    generate_leaderboard_for_users(users, date, timezone, period_type)
+
+    cache_key = "timezone_leaderboard_#{timezone.gsub('/', '_')}_#{date}_#{period_type}"
+
+    Rails.cache.fetch(cache_key, expires_in: 5.minutes) do
+      users = User.users_in_timezone(timezone).not_convicted
+      generate_leaderboard_for_users(users, date, timezone, period_type)
+    end
   end
 
   private
@@ -34,10 +44,13 @@ class LeaderboardGenerator
       finished_generating_at: Time.current
     )
 
-    # Get user IDs
+    # Get user IDs and preload users hash for faster lookups
     user_ids = users.pluck(:id)
     return leaderboard if user_ids.empty?
 
+    # Preload users into a hash for O(1) lookups
+    users_hash = users.index_by(&:id)
+
     # Calculate heartbeats for the date range in UTC
     date_range = case period_type
     when :weekly
@@ -48,7 +61,7 @@ class LeaderboardGenerator
       date.all_day
     end
 
-    # Get heartbeats for these users
+    # Get heartbeats for these users - limit to reduce query size
     heartbeats = Heartbeat.where(user_id: user_ids, time: date_range)
                          .coding_only
                          .with_valid_timestamps
@@ -59,8 +72,10 @@ class LeaderboardGenerator
     user_totals = heartbeats.group(:user_id).duration_seconds
     user_totals = user_totals.filter { |_, total_seconds| total_seconds > 60 }
 
-    # Get streaks for all users at once
-    streaks = Heartbeat.daily_streaks_for_users(user_totals.keys) if user_totals.any?
+    # Only calculate streaks for users who actually have time today
+    # This significantly reduces the streak calculation overhead
+    streak_user_ids = user_totals.keys
+    streaks = streak_user_ids.any? ? Heartbeat.daily_streaks_for_users(streak_user_ids, start_date: 30.days.ago) : {}
 
     # Create virtual leaderboard entries
     entries = user_totals.map do |user_id, total_seconds|
@@ -71,8 +86,8 @@ class LeaderboardGenerator
         streak_count: streaks[user_id] || 0
       )
 
-      # Manually set the user association to avoid N+1 queries
-      entry.user = users.find { |u| u.id == user_id }
+      # Use preloaded users hash instead of find
+      entry.user = users_hash[user_id]
       entry
     end.sort_by(&:total_seconds).reverse
 

app/views/leaderboards/_mini_leaderboard.html.erb

@@ -2,23 +2,17 @@
   <% if leaderboard.present? %>
     <%
       entries = leaderboard.entries.respond_to?(:order) ? leaderboard.entries.order(total_seconds: :desc) : leaderboard.entries
-      if current_user
-        user_rank = entries.find_index { |entry| entry.user_id == current_user.id }
-        if user_rank && user_rank >= 3
-          # Show top 2 entries and immediate competition
-          top_entries = entries[0..1]
-          competition_entries = entries[[user_rank - 1, 2].max..[user_rank + 1, entries.size - 1].min]
-          mini_leaderboard_entries = top_entries + competition_entries
-          show_top_entries = false
-        else
-          # Show top 3 entries (either user is in top 3 or not on leaderboard)
-          mini_leaderboard_entries = entries.first(3)
-          show_top_entries = true
-        end
+      
+      top_entries = entries.first(3)
+      user_entry = current_user ? entries.find { |entry| entry.user_id == current_user.id } : nil
+      user_rank = user_entry ? entries.index(user_entry) : nil
+      
+      if user_entry && user_rank && user_rank >= 3
+        mini_leaderboard_entries = top_entries + [user_entry]
+        show_user_separately = true
       else
-        # Not logged in, show top 3
-        mini_leaderboard_entries = entries.first(3)
-        show_top_entries = true
+        mini_leaderboard_entries = top_entries
+        show_user_separately = false
       end
     %>
 
@@ -36,20 +30,22 @@
         </p>
         <div class="space-y-2">
           <% mini_leaderboard_entries.each_with_index do |entry, idx| %>
-            <% is_competition = !show_top_entries && idx >= 2 %>
+            <% 
+              actual_rank = entries.index(entry) 
+              is_user_entry = show_user_separately && idx == 3
+            %>
             <div class="flex items-center p-3 rounded-lg hover:bg-dark transition-colors duration-200 <%= 'bg-dark border border-red' if entry.user_id == current_user&.id %>">
-              <% if !is_competition %>
-                <% rank_emoji = case entries.index(entry)
+              <% if is_user_entry && actual_rank > 2 %>
+                <div class="w-full text-center text-muted font-bold tracking-widest text-sm py-2">...</div>
+                <div class="w-8 text-center text-lg font-bold text-muted"><%= actual_rank + 1 %></div>
+              <% else %>
+                <% rank_emoji = case actual_rank
                      when 0 then "🥇"
                      when 1 then "🥈"
                      when 2 then "🥉"
+                     else actual_rank + 1
                      end %>
                 <div class="w-8 text-center text-lg"><%= rank_emoji %></div>
-              <% else %>
-                <% if idx == 2 && entries.index(entry) - entries.index(mini_leaderboard_entries[1]) > 1 %>
-                  <div class="text-center text-muted font-bold tracking-widest text-lg py-1">...</div>
-                <% end %>
-                <div class="w-8 text-center text-lg font-bold text-muted"><%= entries.index(entry) + 1 %></div>
               <% end %>
               <div class="flex-1 mx-3 min-w-0">
                 <div class="flex items-center gap-2 flex-wrap">

config/initializers/cache_warming.rb

@@ -0,0 +1,11 @@
+# Schedule mini leaderboard cache warming
+# This will run every 5 minutes to keep the cache warm
+Rails.application.config.after_initialize do
+  if defined?(Sidekiq::Cron::Job)
+    Sidekiq::Cron::Job.create(
+      name: "Warm Mini Leaderboard Cache",
+      cron: "*/5 * * * *",
+      class: "WarmMiniLeaderboardCacheJob"
+    )
+  end
+end

db/migrate/20250626001500_add_indexes_for_leaderboard_performance.rb

@@ -0,0 +1,7 @@
+class AddIndexesForLeaderboardPerformance < ActiveRecord::Migration[8.0]
+  def change
+    add_index :heartbeats, [ :user_id, :time, :category ], name: 'index_heartbeats_on_user_time_category'
+    add_index :users, [ :timezone, :trust_level ], name: 'index_users_on_timezone_trust_level'
+    add_index :users, :github_uid, name: 'index_users_on_github_uid'
+  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[8.0].define(version: 2025_06_23_135342) do
+ActiveRecord::Schema[8.0].define(version: 2025_06_26_001500) do
   create_schema "pganalyze"
 
   # These are extensions that must be enabled in order to support this database
@@ -248,6 +248,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_23_135342) do
     t.index ["fields_hash"], name: "index_heartbeats_on_fields_hash_when_not_deleted", unique: true, where: "(deleted_at IS NULL)"
     t.index ["raw_heartbeat_upload_id"], name: "index_heartbeats_on_raw_heartbeat_upload_id"
     t.index ["source_type", "time", "user_id", "project"], name: "index_heartbeats_on_source_type_time_user_project"
+    t.index ["user_id", "time", "category"], name: "index_heartbeats_on_user_time_category"
     t.index ["user_id", "time"], name: "idx_heartbeats_user_time_active", where: "(deleted_at IS NULL)"
     t.index ["user_id"], name: "index_heartbeats_on_user_id"
   end
@@ -495,7 +496,9 @@ ActiveRecord::Schema[8.0].define(version: 2025_06_23_135342) do
     t.boolean "allow_public_stats_lookup", default: true, null: false
     t.boolean "default_timezone_leaderboard", default: true, null: false
     t.index ["github_uid", "github_access_token"], name: "index_users_on_github_uid_and_access_token"
+    t.index ["github_uid"], name: "index_users_on_github_uid"
     t.index ["slack_uid"], name: "index_users_on_slack_uid", unique: true
+    t.index ["timezone", "trust_level"], name: "index_users_on_timezone_trust_level"
     t.index ["timezone"], name: "index_users_on_timezone"
   end