1 files changed, 37 insertions, 0 deletions
diff --git a/app/models/ci/namespace_mirror.rb b/app/models/ci/namespace_mirror.rb
new file mode 100644
index 00000000000..8a4be3139e8
--- /dev/null
+++ b/app/models/ci/namespace_mirror.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module Ci
+  # This model represents a record in a shadow table of the main database's namespaces table.
+  # It allows us to navigate the namespace hierarchy on the ci database without resorting to a JOIN.
+  class NamespaceMirror < ApplicationRecord
+    belongs_to :namespace
+
+    scope :contains_namespace, -> (id) do
+      where('traversal_ids @> ARRAY[?]::int[]', id)
+    end
+
+    class << self
+      def sync!(event)
+        namespace = event.namespace
+        traversal_ids = namespace.self_and_ancestor_ids(hierarchy_order: :desc)
+
+        upsert({ namespace_id: event.namespace_id, traversal_ids: traversal_ids },
+               unique_by: :namespace_id)
+
+        # It won't be necessary once we remove `sync_traversal_ids`.
+        # More info: https://gitlab.com/gitlab-org/gitlab/-/issues/347541
+        sync_children_namespaces!(event.namespace_id, traversal_ids)
+      end
+
+      private
+
+      def sync_children_namespaces!(namespace_id, traversal_ids)
+        contains_namespace(namespace_id)
+          .where.not(namespace_id: namespace_id)
+          .update_all(
+            "traversal_ids = ARRAY[#{sanitize_sql(traversal_ids.join(','))}]::int[] || traversal_ids[array_position(traversal_ids, #{sanitize_sql(namespace_id)}) + 1:]"
+          )
+      end
+    end
+  end
+end