[Multiple issue assignees] Elasticsearch for multiple assignees in issue

app/models/concerns/elastic/issues_search.rb

@@ -17,7 +17,14 @@ module Elastic
         indexes :state,       type: :text
         indexes :project_id,  type: :integer
         indexes :author_id,   type: :integer
+
+        # The field assignee_id does not exist in issues table anymore.
+        # Nevertheless we'll keep this field as is because we don't want users to rebuild index
+        # + the ES treats arrays transparently so
+        # to any integer field you can write any array of integers and you don't have to change mapping.
+        # More over you can query those items just like a single integer value.
         indexes :assignee_id, type: :integer
+
         indexes :confidential, type: :boolean
       end
 
@@ -26,10 +33,12 @@ module Elastic
 
         # We don't use as_json(only: ...) because it calls all virtual and serialized attributtes
         # https://gitlab.com/gitlab-org/gitlab-ee/issues/349
-        [:id, :iid, :title, :description, :created_at, :updated_at, :state, :project_id, :author_id, :assignee_id, :confidential].each do |attr|
+        [:id, :iid, :title, :description, :created_at, :updated_at, :state, :project_id, :author_id, :confidential].each do |attr|
           data[attr.to_s] = safely_read_attribute_for_elasticsearch(attr)
         end
 
+        data['assignee_id'] = safely_read_attribute_for_elasticsearch(:assignee_ids)
+
         data
       end
 

app/models/concerns/elastic/notes_search.rb

@@ -34,7 +34,7 @@ module Elastic
 
         if noteable.is_a?(Issue)
           data['issue'] = {
-            assignee_id: noteable.assignee_id,
+            assignee_id: noteable.assignee_ids,
             author_id: noteable.author_id,
             confidential: noteable.confidential
           }

app/models/issue_assignee.rb

 class IssueAssignee < ActiveRecord::Base
+  extend Gitlab::CurrentSettings
+
   belongs_to :issue
   belongs_to :assignee, class_name: "User", foreign_key: :user_id
 
   after_create :update_assignee_cache_counts
   after_destroy :update_assignee_cache_counts
 
+  # EE-specific
+  after_create :update_elasticsearch_index
+  after_destroy :update_elasticsearch_index
+  # EE-specific
+
   def update_assignee_cache_counts
     assignee&.update_cache_counts
   end
+
+  def update_elasticsearch_index
+    if current_application_settings.elasticsearch_indexing?
+      ElasticIndexerWorker.perform_async(
+        :update,
+        'Issue',
+        issue.id,
+        changed_fields: ['assignee_ids']
+      )
+    end
+  end
 end

app/workers/elastic_indexer_worker.rb

@@ -5,7 +5,7 @@ class ElasticIndexerWorker
 
   sidekiq_options queue: :elasticsearch, retry: 2
 
-  ISSUE_TRACKED_FIELDS = %w(assignee_id author_id confidential).freeze
+  ISSUE_TRACKED_FIELDS = %w(assignee_ids author_id confidential).freeze
 
   def perform(operation, class_name, record_id, options = {})
     return true unless current_application_settings.elasticsearch_indexing?

spec/models/concerns/elastic/issue_spec.rb

@@ -35,7 +35,9 @@ describe Issue, elastic: true do
 
     expected_hash = issue.attributes.extract!('id', 'iid', 'title', 'description', 'created_at',
                                                 'updated_at', 'state', 'project_id', 'author_id',
-                                                'assignee_id', 'confidential')
+                                                'confidential')
+
+    expected_hash['assignee_id'] = []
 
     expect(issue.as_indexed_json).to eq(expected_hash)
   end