PERF: new table used for title similarity search

app/models/search_observer.rb

@@ -35,6 +35,11 @@ class SearchObserver < ActiveRecord::Observer
     # don't allow concurrency to mess up saving a post
   end
 
+  def self.update_topics_index(topic_id, title, cooked)
+    search_data = title.dup << " " << scrub_html_for_search(cooked)[0...Topic::MAX_SIMILAR_BODY_LENGTH]
+    update_index('topic', topic_id, search_data)
+  end
+
   def self.update_posts_index(post_id, cooked, title, category)
     search_data = scrub_html_for_search(cooked) << " " << title
     search_data << " " << category if category
@@ -55,6 +60,7 @@ class SearchObserver < ActiveRecord::Observer
       if obj.topic
         category_name = obj.topic.category.name if obj.topic.category
         SearchObserver.update_posts_index(obj.id, obj.cooked, obj.topic.title, category_name)
+        SearchObserver.update_topics_index(obj.topic_id, obj.topic.title, obj.cooked) if obj.post_number == 1
       else
         Rails.logger.warn("Orphan post skipped in search_observer, topic_id: #{obj.topic_id} post_id: #{obj.id} raw: #{obj.raw}")
       end
@@ -69,6 +75,7 @@ class SearchObserver < ActiveRecord::Observer
         if post
           category_name = obj.category.name if obj.category
           SearchObserver.update_posts_index(post.id, post.cooked, obj.title, category_name)
+          SearchObserver.update_topics_index(obj.id, obj.title, post.cooked)
         end
       end
     end

app/models/topic.rb

@@ -358,12 +358,13 @@ class Topic < ActiveRecord::Base
     archetype == Archetype.private_message
   end
 
+  MAX_SIMILAR_BODY_LENGTH = 200
   # Search for similar topics
   def self.similar_to(title, raw, user=nil)
     return [] unless title.present?
     return [] unless raw.present?
 
-    filter_words = Search.prepare_data(title + " " + raw[0...200]);
+    filter_words = Search.prepare_data(title + " " + raw[0...MAX_SIMILAR_BODY_LENGTH]);
     ts_query = Search.ts_query(filter_words, nil, "|")
 
     # Exclude category definitions from similar topic suggestions
@@ -371,8 +372,7 @@ class Topic < ActiveRecord::Base
     candidates = Topic.visible
        .secured(Guardian.new(user))
        .listable_topics
-       .joins('JOIN posts p ON p.topic_id = topics.id AND p.post_number = 1')
+       .joins('JOIN topic_search_data s ON topics.id = s.topic_id')
-       .joins('JOIN post_search_data s ON p.id = s.post_id')
        .where("search_data @@ #{ts_query}")
        .order("ts_rank(search_data, #{ts_query}) DESC")
        .limit(SiteSetting.max_similar_results * 3)

db/migrate/20140808051823_create_topic_search_index.rb

@@ -0,0 +1,17 @@
+class CreateTopicSearchIndex < ActiveRecord::Migration
+  def up
+    # used for similarity search
+    create_table :topic_search_data, id: false do |t|
+      t.integer :topic_id, null: false, primary_key: true
+      t.text :raw_data
+      t.string :locale, null: false
+      t.tsvector :search_data
+    end
+
+    execute "CREATE INDEX idx_search_topic ON topic_search_data USING gin (search_data)"
+  end
+
+  def down
+    drop_table :topic_search_data
+  end
+end

lib/search.rb

@@ -55,6 +55,19 @@ class Search
       SearchObserver.index(post)
     end
 
+    posts = Post.joins(:topic)
+            .where('posts.id IN (
+               SELECT p2.id FROM posts p2
+               LEFT JOIN topic_search_data pd ON locale = ? AND p2.topic_id = pd.topic_id
+               WHERE pd.topic_id IS NULL AND p2.post_number = 1
+              )', SiteSetting.default_locale).limit(10000)
+
+    posts.each do |post|
+      # force indexing
+      post.cooked += " "
+      SearchObserver.index(post)
+    end
+
     nil
   end
 

lib/tasks/search.rake

@@ -3,7 +3,7 @@ task "search:reindex" => :environment do
     puts "Reindexing #{db}"
     puts ""
     puts "Posts:"
-    Post.exec_sql("select p.id, p.cooked, c.name category, t.title from
+    Post.exec_sql("select p.id, p.cooked, c.name category, t.title, p.post_number, t.id topic_id from
                    posts p
                    join topics t on t.id = p.topic_id
                    left join categories c on c.id = t.category_id
@@ -12,7 +12,11 @@ task "search:reindex" => :environment do
       cooked = p["cooked"]
       title = p["title"]
       category = p["cat"]
+      post_number = p["post_number"].to_i
+      topic_id = p["topic_id"].to_i
+
       SearchObserver.update_posts_index(post_id, cooked, title, category)
+      SearchObserver.update_topics_index(topic_id, title , cooked) if post_number == 1
 
       putc "."
     end