Avoid using contained by psql operator

app/models/namespaces/traversal/linear.rb

@@ -45,7 +45,6 @@ module Namespaces
         after_update :sync_traversal_ids, if: -> { sync_traversal_ids? && saved_change_to_parent_id? }
 
         scope :traversal_ids_contains, ->(ids) { where("traversal_ids @> (?)", ids) }
-        scope :traversal_ids_contained_by, ->(ids) { where("traversal_ids <@ (?)", ids) }
       end
 
       def sync_traversal_ids?
@@ -102,7 +101,7 @@ module Namespaces
         end
 
         if bottom
-          skope = skope.traversal_ids_contained_by(sql_array(bottom.traversal_ids))
+          skope = skope.where(id: bottom.traversal_ids[0..-1])
         end
 
         # The original `with_depth` attribute in ObjectHierarchy increments as you
@@ -116,10 +115,6 @@ module Namespaces
 
         skope
       end
-
-      def sql_array(ids)
-        "{#{ids.join(',')}}"
-      end
     end
   end
 end

spec/models/group_spec.rb

@@ -454,7 +454,7 @@ RSpec.describe Group do
       end
 
       describe '#ancestors' do
-        it { expect(group.ancestors.to_sql).to include 'traversal_ids <@' }
+        it { expect(group.ancestors.to_sql).to include "\"namespaces\".\"id\" = #{group.parent_id}" }
 
         it 'hierarchy order' do
           expect(group.ancestors(hierarchy_order: :asc).to_sql).to include 'ORDER BY "depth" ASC'

spec/support/shared_examples/namespaces/traversal_examples.rb

@@ -39,16 +39,17 @@ RSpec.shared_examples 'namespace traversal' do
   end
 
   describe '#ancestors' do
-    let(:group) { create(:group) }
-    let(:nested_group) { create(:group, parent: group) }
-    let(:deep_nested_group) { create(:group, parent: nested_group) }
-    let(:very_deep_nested_group) { create(:group, parent: deep_nested_group) }
+    let_it_be(:group) { create(:group) }
+    let_it_be(:nested_group) { create(:group, parent: group) }
+    let_it_be(:deep_nested_group) { create(:group, parent: nested_group) }
+    let_it_be(:very_deep_nested_group) { create(:group, parent: deep_nested_group) }
 
     it 'returns the correct ancestors' do
-      expect(very_deep_nested_group.ancestors).to include(group, nested_group, deep_nested_group)
-      expect(deep_nested_group.ancestors).to include(group, nested_group)
-      expect(nested_group.ancestors).to include(group)
-      expect(group.ancestors).to eq([])
+      # #reload is called to make sure traversal_ids are reloaded
+      expect(very_deep_nested_group.reload.ancestors).to contain_exactly(group, nested_group, deep_nested_group)
+      expect(deep_nested_group.reload.ancestors).to contain_exactly(group, nested_group)
+      expect(nested_group.reload.ancestors).to contain_exactly(group)
+      expect(group.reload.ancestors).to eq([])
     end
 
     describe '#recursive_ancestors' do