FIX: Exclude unlisted topics from hot scores (#37312)

Unlisted topics (visible=false) should not appear in hot topic
rankings. This change:

- Filters out unlisted topics when updating hot scores
- Excludes unlisted topics from hottest_topic_ids cache
- Applies 50% score reduction to closed topics
- Removes unlisted topics from index

app/models/topic_hot_score.rb

@@ -11,7 +11,11 @@ class TopicHotScore < ActiveRecord::Base
   end
 
   def self.recreate_hottest_topic_ids_cache
-    hot_topics = Topic.where(archetype: Archetype.default).where.not(id: Category.topic_ids)
+    hot_topics =
+      Topic
+        .where(archetype: Archetype.default)
+        .where(visible: true)
+        .where.not(id: Category.topic_ids)
 
     # 10% of the topics with activity since the hot topics cutoff.
     limit =
@@ -77,6 +81,7 @@ class TopicHotScore < ActiveRecord::Base
         AND topics.deleted_at IS NULL
         AND topics.archetype <> :private_message
         AND topics.created_at <= :now
+        AND topics.visible = true
       ORDER BY
         CASE WHEN topics.pinned_at IS NOT NULL THEN 0 ELSE 1 END ASC,
         topics.bumped_at desc
@@ -118,6 +123,7 @@ class TopicHotScore < ActiveRecord::Base
               p.created_at >= :recent_cutoff
               AND t.archetype <> 'private_message'
               AND t.deleted_at IS NULL
+              AND t.visible = true
               AND p.deleted_at IS NULL
               AND p.user_deleted = false
               AND t.created_at <= :now
@@ -154,17 +160,19 @@ class TopicHotScore < ActiveRecord::Base
         ) X
       )
       UPDATE topic_hot_scores ths
-      SET score = (
-        CASE WHEN topics.created_at > :recent_cutoff
-          THEN ths.recent_likes ELSE topics.like_count END
-        ) /
-        (EXTRACT(EPOCH FROM (:now - topics.created_at)) / 3600 + 2) ^ :gravity
- +
-        CASE WHEN ths.recent_first_bumped_at IS NULL THEN 0 ELSE
-          (ths.recent_likes + ths.recent_posters - 1) /
-          (EXTRACT(EPOCH FROM (:now - recent_first_bumped_at)) / 3600 + 2) ^ :gravity
-        END
-        ,
+      SET score = CASE WHEN topics.visible = false THEN 0 ELSE
+        ((
+          CASE WHEN topics.created_at > :recent_cutoff
+            THEN ths.recent_likes ELSE topics.like_count END
+          ) /
+          (EXTRACT(EPOCH FROM (:now - topics.created_at)) / 3600 + 2) ^ :gravity
+   +
+          CASE WHEN ths.recent_first_bumped_at IS NULL THEN 0 ELSE
+            (ths.recent_likes + ths.recent_posters - 1) /
+            (EXTRACT(EPOCH FROM (:now - recent_first_bumped_at)) / 3600 + 2) ^ :gravity
+          END
+        ) * CASE WHEN topics.closed THEN 0.5 ELSE 1 END
+        END,
         updated_at = :now
 
       FROM topics

app/services/topic_status_updater.rb

@@ -85,6 +85,8 @@ TopicStatusUpdater =
         CategoryFeaturedTopic.where(topic_id: topic.id).delete_all
       end
 
+      TopicHotScore.where(topic_id: topic.id).delete_all if status.visible? && status.disabled?
+
       result
     end
 

db/migrate/20260126204830_cleanup_unlisted_topic_hot_scores.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+class CleanupUnlistedTopicHotScores < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL
+      DELETE FROM topic_hot_scores
+      WHERE topic_id IN (
+        SELECT id FROM topics WHERE visible = false
+      )
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

spec/models/topic_hot_scores_spec.rb

@@ -193,5 +193,62 @@ RSpec.describe TopicHotScore do
 
       expect(hottest_ids).not_to include(category_topic.id)
     end
+
+    it "applies faster decay to closed topics" do
+      freeze_time
+
+      open_topic = Fabricate(:topic, like_count: 10, created_at: 2.weeks.ago)
+      closed_topic = Fabricate(:topic, like_count: 10, created_at: 2.weeks.ago, closed: true)
+
+      TopicHotScore.update_scores
+
+      open_score = TopicHotScore.find_by(topic_id: open_topic.id).score
+      closed_score = TopicHotScore.find_by(topic_id: closed_topic.id).score
+
+      expect(closed_score).to be < open_score
+      expect(closed_score).to be_within(0.0001).of(open_score * 0.5)
+    end
+
+    it "does not create hot scores for unlisted topics" do
+      freeze_time
+
+      unlisted_topic = Fabricate(:topic, visible: false, like_count: 10, created_at: 1.day.ago)
+
+      TopicHotScore.update_scores
+
+      expect(TopicHotScore.find_by(topic_id: unlisted_topic.id)).to be_nil
+    end
+
+    it "excludes unlisted topics from hottest_topic_ids cache" do
+      freeze_time
+
+      unlisted_topic =
+        Fabricate(
+          :topic,
+          visible: false,
+          like_count: 100,
+          created_at: 1.day.ago,
+          last_posted_at: 10.minutes.ago,
+        )
+      TopicHotScore.create!(topic_id: unlisted_topic.id, score: 999.0)
+
+      TopicHotScore.recreate_hottest_topic_ids_cache
+
+      expect(TopicHotScore.hottest_topic_ids).not_to include(unlisted_topic.id)
+    end
+
+    it "sets score to 0 for unlisted topics during update" do
+      freeze_time
+
+      topic = Fabricate(:topic, like_count: 10, created_at: 2.weeks.ago)
+      TopicHotScore.update_scores
+
+      expect(TopicHotScore.find_by(topic_id: topic.id).score).to be > 0
+
+      topic.update!(visible: false)
+      TopicHotScore.update_scores
+
+      expect(TopicHotScore.find_by(topic_id: topic.id).score).to eq(0)
+    end
   end
 end

spec/services/topic_status_updater_spec.rb

@@ -269,5 +269,14 @@ RSpec.describe TopicStatusUpdater do
       expect(topic.visible).to eq(true)
       expect(topic.visibility_reason_id).to eq(Topic.visibility_reasons[:manually_relisted])
     end
+
+    it "deletes hot score when topic is unlisted" do
+      topic = Fabricate(:topic)
+      TopicHotScore.create!(topic_id: topic.id, score: 1.0)
+
+      TopicStatusUpdater.new(topic, admin).update!("visible", false)
+
+      expect(TopicHotScore.find_by(topic_id: topic.id)).to be_nil
+    end
   end
 end