Preload queries for ListService and use SQL to filter authorized issues

app/services/issue_links/list_service.rb

@@ -26,14 +26,16 @@ module IssueLinks
     def issues
       return @issues if defined?(@issues)
 
+      authorized_issues = IssuesFinder.new(@current_user, project_id: @project.id).execute
       referenced_issues = @issue.referenced_issues.select('issues.*', 'issue_links.id AS issue_links_id')
       referred_by_issues = @issue.referred_by_issues.select('issues.*', 'issue_links.id AS issue_links_id')
-      union = Gitlab::SQL::Union.new([referenced_issues, referred_by_issues])
 
-      sql = "#{union.to_sql} ORDER BY issue_links_id"
+      union = Gitlab::SQL::Union.new([referenced_issues, referred_by_issues])
 
-      @issues = Issue.find_by_sql(sql)
-      @issues = Ability.issues_readable_by_user(@issues, @current_user)
+      @issues = Issue.from("(#{union.to_sql}) #{Issue.table_name}")
+                     .where(id: authorized_issues.select(:id))
+                     .preload(project: :namespace)
+                     .reorder('issue_links_id')
     end
 
     def destroy_relation_path(issue)

spec/services/issue_links/list_service_spec.rb

@@ -38,7 +38,7 @@ describe IssueLinks::ListService, service: true do
 
       it 'verifies number of queries' do
         recorded = ActiveRecord::QueryRecorder.new { subject }
-        expect(recorded.count).to be_within(1).of(42)
+        expect(recorded.count).to be_within(1).of(46)
       end
 
       it 'returns related issues JSON' do