Simplify sql for sorting

app/models/concerns/issuable.rb

@@ -38,7 +38,7 @@ module Issuable
     scope :order_milestone_due_desc, -> { joins(:milestone).reorder('milestones.due_date DESC, milestones.id DESC') }
     scope :order_milestone_due_asc, -> { joins(:milestone).reorder('milestones.due_date ASC, milestones.id ASC') }
     scope :without_label, -> { joins("LEFT OUTER JOIN label_links ON label_links.target_type = '#{name}' AND label_links.target_id = #{table_name}.id").where(label_links: { id: nil }) }
-    scope :order_weight_desc,  -> { reorder('CASE WHEN weight IS NULL then 0 ELSE 1 END DESC, weight DESC') }
+    scope :order_weight_desc, -> { reorder('weight IS NOT NULL, weight DESC') }
     scope :order_weight_asc, -> { reorder('weight ASC') }
 
     scope :join_project, -> { joins(:project) }

spec/models/concerns/issuable_spec.rb

@@ -115,21 +115,23 @@ describe Issue, "Issuable" do
   end
 
   describe "#sort" do
-    let!(:issue)  { create(:issue) }
-    let(:project) { issue.project }
-    let!(:issue2) { create(:issue, weight: 1, project: project) }
-    let!(:issue3) { create(:issue, weight: 2, project: project) }
-    let!(:issue4) { create(:issue, weight: 3, project: project) }
+    let(:project) { build_stubbed(:empty_project) }
 
-    it "sorts by weight desc" do
-      issues = Issue.where(project_id: project.id).sort('weight_desc')
-      expect(issues).to match_array([issue4, issue3, issue2, issue])
-    end
+    context "by weight" do
+      let!(:issue)  { create(:issue, project: project) }
+      let!(:issue2) { create(:issue, weight: 1, project: project) }
+      let!(:issue3) { create(:issue, weight: 2, project: project) }
+      let!(:issue4) { create(:issue, weight: 3, project: project) }
 
+      it "sorts desc" do
+        issues = project.issues.sort('weight_desc')
+        expect(issues).to match_array([issue4, issue3, issue2, issue])
+      end
 
-    it "sorts by weight asc" do
-      issues = Issue.where(project_id: project.id).sort('weight_asc')
-      expect(issues).to match_array([issue2, issue3, issue4, issue])
+      it "sorts asc" do
+        issues = project.issues.sort('weight_asc')
+        expect(issues).to match_array([issue2, issue3, issue4, issue])
+      end
     end
   end