Add hashtag score for better sorting of autosuggestions (#11427)

* Add hashtag score for better sorting of autosuggestions

* Do not use `~<~` operator with no text_pattern_ops index

app/models/tag.rb

@@ -7,6 +7,7 @@
 #  name       :string           default(""), not null
 #  created_at :datetime         not null
 #  updated_at :datetime         not null
+#  score      :integer
 #
 
 class Tag < ApplicationRecord
@@ -78,7 +79,7 @@ class Tag < ApplicationRecord
       pattern = sanitize_sql_like(normalize(term.strip)) + '%'
 
       Tag.where(arel_table[:name].lower.matches(pattern.mb_chars.downcase.to_s))
-         .order(:name)
+         .order(Arel.sql('length(name) ASC, score DESC, name ASC'))
          .limit(limit)
          .offset(offset)
     end

app/models/trending_tags.rb

@@ -48,12 +48,17 @@ class TrendingTags
         redis.zrem(key, tag_id.to_s)
       else
         score = ((observed - expected)**2) / expected
-        redis.zadd(key, score, tag_id.to_s)
+        added = redis.zadd(key, score, tag_id.to_s)
+        bump_tag_score!(tag_id) if added == 1
       end
 
       redis.expire(key, EXPIRE_TRENDS_AFTER)
     end
 
+    def bump_tag_score!(tag_id)
+      Tag.where(id: tag_id).update_all('score = COALESCE(score, 0) + 1')
+    end
+
     def disallowed_hashtags
       return @disallowed_hashtags if defined?(@disallowed_hashtags)