1 files changed, 48 insertions, 0 deletions
diff --git a/lib/gitlab/work_items/work_item_hierarchy.rb b/lib/gitlab/work_items/work_item_hierarchy.rb
new file mode 100644
index 00000000000..e71bf2bce6a
--- /dev/null
+++ b/lib/gitlab/work_items/work_item_hierarchy.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module WorkItems
+    class WorkItemHierarchy < ObjectHierarchy
+      extend ::Gitlab::Utils::Override
+
+      private
+
+      def middle_table
+        ::WorkItems::ParentLink.arel_table
+      end
+
+      def from_tables(cte)
+        [objects_table, cte.table, middle_table]
+      end
+
+      override :parent_id_column
+      def parent_id_column(cte)
+        middle_table[:work_item_parent_id]
+      end
+
+      override :ancestor_conditions
+      def ancestor_conditions(cte)
+        conditions = middle_table[:work_item_parent_id].eq(objects_table[:id]).and(
+          middle_table[:work_item_id].eq(cte.table[:id])
+        )
+
+        with_type_filter(conditions, cte)
+      end
+
+      override :descendant_conditions
+      def descendant_conditions(cte)
+        conditions = middle_table[:work_item_id].eq(objects_table[:id]).and(
+          middle_table[:work_item_parent_id].eq(cte.table[:id])
+        )
+
+        with_type_filter(conditions, cte)
+      end
+
+      def with_type_filter(conditions, cte)
+        return conditions unless options[:same_type]
+
+        conditions.and(objects_table[:work_item_type_id].eq(cte.table[:work_item_type_id]))
+      end
+    end
+  end
+end