Create CTE query for clusters hierarchy

- This enables us to use a scope to query all clusters in group
hierarchy order in one query, and also enables us to union to instance
clusters later.

- Handle case where clusters not present at level. In which case the
query should go ahead and return the next level's clusters.

- Swap with new CTE query behind Feature flag. This FF is default
disabled.

1 files changed, 17 insertions, 2 deletions

diff --git a/app/models/concerns/deployment_platform.rb b/app/models/concerns/deployment_platform.rb
index 5a358ae2ef6..8f28c897eb6 100644
--- a/app/models/concerns/deployment_platform.rb
+++ b/app/models/concerns/deployment_platform.rb
@@ -12,11 +12,26 @@ module DeploymentPlatform
   private
 
   def find_deployment_platform(environment)
-    find_cluster_platform_kubernetes(environment: environment) ||
-      find_group_cluster_platform_kubernetes(environment: environment) ||
+    find_platform_kubernetes(environment) ||
       find_instance_cluster_platform_kubernetes(environment: environment)
   end
 
+  def find_platform_kubernetes(environment)
+    if Feature.enabled?(:clusters_cte)
+      find_platform_kubernetes_with_cte(environment)
+    else
+      find_cluster_platform_kubernetes(environment: environment) ||
+        find_group_cluster_platform_kubernetes(environment: environment)
+    end
+  end
+
+  # EE would override this and utilize environment argument
+  def find_platform_kubernetes_with_cte(_environment)
+    Clusters::ClustersHierarchy.new(self).base_and_ancestors
+      .enabled.default_environment
+      .first&.platform_kubernetes
+  end
+
   # EE would override this and utilize environment argument
   def find_cluster_platform_kubernetes(environment: nil)
     clusters.enabled.default_environment