Fix project db query for GraphQL pagination

Due to a calculation for ordering the projects on the usage quota page
in the storage tab, the GraphQL pagination returned wrong results on the
next page click. This change will introduce a new logic in the GraphQL
pagination especially for the order for this query.

ee/app/models/ee/project.rb

@@ -165,13 +165,14 @@ module EE
       scope :without_repository_size_limit, -> { where(repository_size_limit: nil) }
 
       scope :order_by_total_repository_size_excess_desc, -> (limit) do
-        excess = ::ProjectStatistics.arel_table[:repository_size] +
+        excess_arel = ::ProjectStatistics.arel_table[:repository_size] +
                    ::ProjectStatistics.arel_table[:lfs_objects_size] -
-                   ::Project.arel_table.coalesce(::Project.arel_table[:repository_size_limit], limit, 0)
+                   arel_table.coalesce(arel_table[:repository_size_limit], limit, 0)
+        alias_node = Arel::Nodes::SqlLiteral.new('excess_storage')
 
-        joins(:statistics).order(
-          Arel.sql(Arel::Nodes::Descending.new(excess).to_sql)
-        )
+        select(*arel.projections, excess_arel.as(alias_node))
+          .joins(:statistics)
+          .order(excess_arel.desc)
       end
 
       delegate :shared_runners_minutes, :shared_runners_seconds, :shared_runners_seconds_last_reset,

ee/lib/ee/gitlab/graphql/pagination/keyset/order_info.rb

+# frozen_string_literal: true
+
+module EE
+  module Gitlab
+    module Graphql
+      module Pagination
+        module Keyset
+          module OrderInfo
+            extend ::Gitlab::Utils::Override
+
+            private
+
+            override :extract_attribute_values
+            def extract_attribute_values(order_value)
+              if ordering_by_excess_storage?(order_value)
+                ['excess_storage', order_value.direction, order_value.expr]
+              else
+                super
+              end
+            end
+
+            # determine if ordering using STORAGE
+            def ordering_by_excess_storage?(order_value)
+              order_value.expr.is_a?(Arel::Nodes::Grouping) &&
+                order_value.to_sql.delete('"').include?('(project_statistics.repository_size + project_statistics.lfs_objects_size)')
+            end
+          end
+        end
+      end
+    end
+  end
+end

ee/spec/lib/gitlab/graphql/pagination/keyset/order_info_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Graphql::Pagination::Keyset::OrderInfo do
+  describe '#build_order_list' do
+    let(:order_list) { described_class.build_order_list(relation) }
+
+    context 'when ordering by STORAGE' do
+      let(:relation) { Project.order_by_total_repository_size_excess_desc(10.gigabytes) }
+
+      it 'assigns the right attribute name, named function, and direction' do
+        expect(order_list.count).to eq 1
+        expect(order_list.first.attribute_name).to eq 'excess_storage'
+        expect(order_list.first.named_function).to be_kind_of(Arel::Nodes::Grouping)
+        expect(order_list.first.named_function.to_sql.delete('"')).to include '(project_statistics.repository_size + project_statistics.lfs_objects_size)'
+        expect(order_list.first.sort_direction).to eq :desc
+      end
+    end
+  end
+end

lib/gitlab/graphql/pagination/keyset/order_info.rb

@@ -127,3 +127,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::Graphql::Pagination::Keyset::OrderInfo.prepend_if_ee('EE::Gitlab::Graphql::Pagination::Keyset::OrderInfo')