PERF: Add partial index for non-pm search.

app/services/search_indexer.rb

@@ -85,6 +85,7 @@ class SearchIndexer
       "search_data" => tsvector,
     }
 
+    yield params if block_given?
     table_name.camelize.constantize.upsert(params)
   rescue => e
     if Rails.env.test?
@@ -111,7 +112,7 @@ class SearchIndexer
     )
   end
 
-  def self.update_posts_index(post_id, topic_title, category_name, topic_tags, cooked)
+  def self.update_posts_index(post_id:, topic_title:, category_name:, topic_tags:, cooked:, private_message:)
     update_index(
       table: 'post',
       id: post_id,
@@ -119,7 +120,9 @@ class SearchIndexer
       b_weight: category_name,
       c_weight: topic_tags,
       d_weight: scrub_html_for_search(cooked)
-    )
+    ) do |params|
+      params["private_message"] = private_message
+    end
   end
 
   def self.update_users_index(user_id, username, name)
@@ -204,7 +207,15 @@ class SearchIndexer
        )
 
       if topic
-        SearchIndexer.update_posts_index(obj.id, topic.title, category_name, tag_names, obj.cooked)
+        SearchIndexer.update_posts_index(
+          post_id: obj.id,
+          topic_title: topic.title,
+          category_name: category_name,
+          topic_tags: tag_names,
+          cooked: obj.cooked,
+          private_message: topic.private_message?
+        )
+
         SearchIndexer.update_topics_index(topic.id, topic.title, obj.cooked) if obj.is_first_post?
       end
     end
@@ -216,7 +227,15 @@ class SearchIndexer
     if Topic === obj && (obj.saved_change_to_title? || force)
       if obj.posts
         if post = obj.posts.find_by(post_number: 1)
-          SearchIndexer.update_posts_index(post.id, obj.title, category_name, tag_names, post.cooked)
+          SearchIndexer.update_posts_index(
+            post_id: post.id,
+            topic_title: obj.title,
+            category_name: category_name,
+            topic_tags: tag_names,
+            cooked: post.cooked,
+            private_message: obj.private_message?
+          )
+
           SearchIndexer.update_topics_index(obj.id, obj.title, post.cooked)
         end
       end

db/migrate/20200813051337_add_private_message_to_post_search_data.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+class AddPrivateMessageToPostSearchData < ActiveRecord::Migration[6.0]
+  def up
+    add_column :post_search_data, :private_message, :boolean
+
+    # Delete post_search_data of orphaned posts
+    execute <<~SQL
+    DELETE FROM post_search_data
+    WHERE post_id IN (
+      SELECT posts.id
+      FROM posts
+      LEFT JOIN topics ON topics.id = posts.topic_id
+      WHERE topics.id IS NULL
+    )
+    SQL
+
+    # Delete orphaned post_search_data
+    execute <<~SQL
+    DELETE FROM post_search_data
+    WHERE post_id IN (
+      SELECT post_search_data.post_id
+      FROM post_search_data
+      LEFT JOIN posts ON posts.id = post_search_data.post_id
+      WHERE posts.id IS NULL
+    )
+    SQL
+
+    execute <<~SQL
+    UPDATE post_search_data
+    SET private_message = true
+    FROM posts
+    INNER JOIN topics ON topics.id = posts.topic_id AND topics.archetype = 'private_message'
+    WHERE posts.id = post_search_data.post_id
+    SQL
+
+    execute <<~SQL
+    UPDATE post_search_data
+    SET private_message = false
+    FROM posts
+    INNER JOIN topics ON topics.id = posts.topic_id AND topics.archetype <> 'private_message'
+    WHERE posts.id = post_search_data.post_id
+    SQL
+
+    change_column_null(:post_search_data, :private_message, false)
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

db/migrate/20200813090811_create_partial_index_on_post_search_data.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class CreatePartialIndexOnPostSearchData < ActiveRecord::Migration[6.0]
+  disable_ddl_transaction!
+
+  def up
+    execute <<~SQL
+    CREATE INDEX CONCURRENTLY idx_regular_post_search_data ON post_search_data USING GIN(search_data) WHERE NOT private_message
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+    DROP INDEX IF EXISTS idx_regular_post_search_data;
+    SQL
+  end
+end

lib/search.rb

@@ -818,22 +818,37 @@ class Search
       .joins("LEFT JOIN categories ON categories.id = topics.category_id")
 
     is_topic_search = @search_context.present? && @search_context.is_a?(Topic)
-
     posts = posts.where("topics.visible") unless is_topic_search
 
     if type_filter === "private_messages" || (is_topic_search && @search_context.private_message?)
-      posts = posts.where("topics.archetype =  ?", Archetype.private_message)
+      posts = posts
+        .where(
+          "topics.archetype = ? AND post_search_data.private_message",
+          Archetype.private_message
+        )
 
       unless @guardian.is_admin?
         posts = posts.private_posts_for_user(@guardian.user)
       end
     elsif type_filter === "all_topics"
-      private_posts = posts.where("topics.archetype = ?", Archetype.private_message)
-      private_posts = private_posts.private_posts_for_user(@guardian.user)
+      private_posts = posts
+        .where(
+          "topics.archetype = ? AND post_search_data.private_message",
+          Archetype.private_message
+          )
+        .private_posts_for_user(@guardian.user)
 
-      posts = posts.where("topics.archetype <> ?", Archetype.private_message).or(private_posts)
+      posts = posts
+        .where(
+          "topics.archetype <> ? AND NOT post_search_data.private_message",
+          Archetype.private_message
+        )
+        .or(private_posts)
     else
-      posts = posts.where("topics.archetype <> ?", Archetype.private_message)
+      posts = posts.where(
+        "topics.archetype <> ? AND NOT post_search_data.private_message",
+        Archetype.private_message
+      )
     end
 
     if @term.present?
@@ -1162,6 +1177,8 @@ class Search
     query.includes(topic: topic_eager_loads)
   end
 
+  private
+
   # Limited for performance reasons since `TS_HEADLINE` is slow when the text
   # document is too long.
   MAX_LENGTH_FOR_HEADLINE = 2500

spec/services/search_indexer_spec.rb

@@ -21,7 +21,14 @@ describe SearchIndexer do
     SiteSetting.default_locale = 'zh_CN'
     data = "你好世界"
 
-    SearchIndexer.update_posts_index(post_id, "", "", "", data)
+    SearchIndexer.update_posts_index(
+      post_id: post_id,
+      topic_title: "",
+      category_name: "",
+      topic_tags: "",
+      cooked: data,
+      private_message: false
+    )
 
     post_search_data = PostSearchData.find_by(post_id: post_id)
 
@@ -95,11 +102,27 @@ describe SearchIndexer do
 
   it 'correctly indexes a post according to version' do
     # Preparing so that they can be indexed to right version
-    SearchIndexer.update_posts_index(post_id, "dummy", "", nil, nil)
+    SearchIndexer.update_posts_index(
+      post_id: post_id,
+      topic_title: "dummy",
+      category_name: "",
+      topic_tags: nil,
+      cooked: nil,
+      private_message: false
+    )
+
     PostSearchData.find_by(post_id: post_id).update!(version: -1)
 
     data = "<a>This</a> is a test"
-    SearchIndexer.update_posts_index(post_id, "", "", nil, data)
+
+    SearchIndexer.update_posts_index(
+      post_id: post_id,
+      topic_title: "",
+      category_name: "",
+      topic_tags: nil,
+      cooked: data,
+      private_message: false
+    )
 
     raw_data, locale, version = PostSearchData.where(post_id: post_id).pluck(:raw_data, :locale, :version)[0]
     expect(raw_data).to eq("This is a test")