FIX: hot not adding recently bumped topics (#25619)

When we insert into the hot set we add things with a score of 0
This means that if hot has more than batch size items in it with a score, then the 0s don't get an initial score

This corrects the situation by always ensuring we re-score:

1. batch size high scoring topics
2. (new) batch size recently bumped topics

* Update spec/models/topic_hot_scores_spec.rb

Co-authored-by: Isaac Janzen <50783505+janzenisaac@users.noreply.github.com>

---------

Co-authored-by: Isaac Janzen <50783505+janzenisaac@users.noreply.github.com>

app/models/topic_hot_score.rb

@@ -102,9 +102,26 @@ class TopicHotScore < ActiveRecord::Base
       WHERE thsOrig.topic_id = ths.topic_id
     SQL
 
-    # update up to BATCH_SIZE records that are out of date based on age
-    # we need an extra index for this
-    DB.exec(<<~SQL, args)
+    # we may end up update 2x batch size, this is ok
+    # we need to update 1 batch of high scoring topics
+    # we need to update a second batch of recently bumped topics
+    sql = <<~SQL
+      WITH topic_ids AS (
+        SELECT topic_id FROM (
+          SELECT th3.topic_id FROM topic_hot_scores th3
+          JOIN topics t3 on t3.id = th3.topic_id
+          ORDER BY t3.bumped_at DESC
+          LIMIT :max
+        ) Y
+
+        UNION ALL
+
+        SELECT topic_id FROM (
+          SELECT th2.topic_id FROM topic_hot_scores th2
+          ORDER BY th2.score DESC, th2.recent_first_bumped_at DESC NULLS LAST
+          LIMIT :max
+        ) X
+      )
       UPDATE topic_hot_scores ths
       SET score = (
         CASE WHEN topics.created_at > :recent_cutoff
@@ -121,11 +138,11 @@ class TopicHotScore < ActiveRecord::Base
 
       FROM topics
       WHERE topics.id IN (
-        SELECT topic_id FROM topic_hot_scores
-        ORDER BY score DESC, recent_first_bumped_at DESC NULLS LAST
-        LIMIT :max
+        SELECT topic_id FROM topic_ids
       ) AND ths.topic_id = topics.id
     SQL
+
+    DB.exec(sql, args)
   end
 end
 

spec/models/topic_hot_scores_spec.rb

@@ -6,6 +6,28 @@ RSpec.describe TopicHotScore do
     fab!(:user2) { Fabricate(:user) }
     fab!(:user3) { Fabricate(:user) }
 
+    it "also always updates based on recent activity" do
+      freeze_time
+
+      # this will come in with a score
+      topic = Fabricate(:topic, created_at: 1.hour.ago, bumped_at: 2.minutes.ago)
+      post = Fabricate(:post, topic: topic, created_at: 2.minute.ago)
+      PostActionCreator.like(user, post)
+
+      TopicHotScore.update_scores
+
+      # this will come in in the batch in score 0
+      topic = Fabricate(:topic, created_at: 1.minute.ago, bumped_at: 1.minute.ago)
+      post = Fabricate(:post, topic: topic, created_at: 1.minute.ago)
+      PostActionCreator.like(user, post)
+
+      # batch size is 1 so if we do not do something special we only update
+      # the high score topic and skip new
+      TopicHotScore.update_scores(1)
+
+      expect(TopicHotScore.find_by(topic_id: topic.id).score).to be_within(0.001).of(0.861)
+    end
+
     it "can correctly update like counts and post counts and account for activity" do
       freeze_time