Merge branch 'bvl-fix-count-with-selects' into 'master'

Remove the selects when counting the last page

Closes #40266

See merge request gitlab-org/gitlab-ce!15456

changelogs/unreleased/bvl-fix-count-with-selects.yml

+---
+title: Fix crash when navigating to second page of the group dashbaord when there
+  are projects and groups on the first page
+merge_request: 15456
+author:
+type: fixed

lib/gitlab/multi_collection_paginator.rb

@@ -55,7 +55,9 @@ module Gitlab
     def first_collection_last_page_size
       return @first_collection_last_page_size if defined?(@first_collection_last_page_size)
 
-      @first_collection_last_page_size = paginated_first_collection(first_collection_page_count).count
+      @first_collection_last_page_size = paginated_first_collection(first_collection_page_count)
+                                           .except(:select)
+                                           .size
     end
   end
 end

spec/controllers/groups/children_controller_spec.rb

@@ -280,6 +280,17 @@ describe Groups::ChildrenController do
 
           expect(assigns(:children)).to contain_exactly(other_subgroup, *next_page_projects.take(per_page - 1))
         end
+
+        context 'with a mixed first page' do
+          let!(:first_page_subgroups) { [create(:group,  :public,  parent: group)] }
+          let!(:first_page_projects) { create_list(:project, per_page, :public, namespace: group) }
+
+          it 'correctly calculates the counts' do
+            get :index, group_id: group.to_param, sort: 'id_asc', page: 2, format: :json
+
+            expect(response).to have_gitlab_http_status(200)
+          end
+        end
       end
     end
   end