Override elasticsearch setting for STI note models

app/models/diff_note.rb

@@ -4,11 +4,6 @@
 #
 # A note of this type can be resolvable.
 class DiffNote < Note
-  # Elastic search configuration (it does not support STI properly)
-  document_type 'note'
-  index_name [Rails.application.class.parent_name.downcase, Rails.env].join('-')
-  include Elastic::NotesSearch
-
   include NoteOnDiff
   include Gitlab::Utils::StrongMemoize
 

doc/update/11.1-to-11.2.md

@@ -357,6 +357,23 @@ sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
 
 If all items are green, then congratulations, the upgrade is complete!
 
+### 16. Elasticsearch index update (if you currently use Elasticsearch)
+
+In 11.2 release we fixed a bug that caused some types of notes to not be indexed. Please re-create your index by using one of two ways listed below:
+
+1. Re-create the index. The following command is acceptable for not very big GitLab instances (storage size no more than few gigabytes).
+
+    ```
+    # Omnibus installations
+    sudo gitlab-rake gitlab:elastic:index
+
+    # Installations from source
+    bundle exec rake gitlab:elastic:index
+    ```
+
+1. For very big GitLab instances we recommend following [Add GitLab's data to the Elasticsearch index](../integration/elasticsearch.md#indexing-large-instances).
+
+
 ## Things went south? Revert to previous version (11.1)
 
 ### 1. Revert the code to the previous version

ee/app/models/concerns/elastic/notes_search.rb

@@ -23,6 +23,14 @@ module Elastic
         indexes :noteable_id,    type: :integer, index: :not_analyzed
       end
 
+      def self.inherited(subclass)
+        super
+
+        subclass.__elasticsearch__.index_name = self.index_name
+        subclass.__elasticsearch__.document_type = self.document_type
+        subclass.__elasticsearch__.instance_variable_set(:@mapping, self.mapping.dup)
+      end
+
       def as_indexed_json(options = {})
         data = {}
 

ee/changelogs/unreleased/elastic-sti-index-name.yml

+---
+title: 'Elasticsearch: Fix a bug causing some types of note to miss being indexed'
+merge_request: 6736
+author:
+type: fixed

ee/spec/models/concerns/elastic/note_spec.rb

@@ -70,6 +70,14 @@ describe Note, :elastic do
     create :note, :system, project: project, noteable: issue
   end
 
+  it 'uses same index for Note subclasses' do
+    Note.subclasses.each do |note_class|
+      expect(note_class.index_name).to eq(Note.index_name)
+      expect(note_class.document_type).to eq(Note.document_type)
+      expect(note_class.mappings.to_hash).to eq(Note.mappings.to_hash)
+    end
+  end
+
   context 'notes to confidential issues' do
     it "does not find note" do
       issue = create :issue, :confidential