Ensure orphaned rows are deleted before adding the foreign key

db/migrate/20180302152117_ensure_foreign_keys_on_clusters_applications.rb

@@ -9,12 +9,28 @@ class EnsureForeignKeysOnClustersApplications < ActiveRecord::Migration
   disable_ddl_transaction!
 
   def up
+    existing = Clusters::Cluster
+      .joins(:application_ingress)
+      .where('clusters.id = clusters_applications_ingress.cluster_id')
+
+    Clusters::Applications::Ingress.where('NOT EXISTS (?)', existing).in_batches do |batch|
+      batch.delete_all
+    end
+
     unless foreign_keys_for(:clusters_applications_ingress, :cluster_id).any?
       add_concurrent_foreign_key :clusters_applications_ingress, :clusters,
         column: :cluster_id,
         on_delete: :cascade
     end
 
+    existing = Clusters::Cluster
+      .joins(:application_prometheus)
+      .where('clusters.id = clusters_applications_prometheus.cluster_id')
+
+    Clusters::Applications::Ingress.where('NOT EXISTS (?)', existing).in_batches do |batch|
+      batch.delete_all
+    end
+
     unless foreign_keys_for(:clusters_applications_prometheus, :cluster_id).any?
       add_concurrent_foreign_key :clusters_applications_prometheus, :clusters,
         column: :cluster_id,

db/schema.rb

@@ -2028,8 +2028,8 @@ ActiveRecord::Schema.define(version: 20180307012445) do
   add_foreign_key "cluster_providers_gcp", "clusters", on_delete: :cascade
   add_foreign_key "clusters", "users", on_delete: :nullify
   add_foreign_key "clusters_applications_helm", "clusters", on_delete: :cascade
-  add_foreign_key "clusters_applications_ingress", "clusters", on_delete: :cascade
-  add_foreign_key "clusters_applications_prometheus", "clusters", on_delete: :cascade
+  add_foreign_key "clusters_applications_ingress", "clusters", name: "fk_753a7b41c1", on_delete: :cascade
+  add_foreign_key "clusters_applications_prometheus", "clusters", name: "fk_557e773639", on_delete: :cascade
   add_foreign_key "clusters_applications_runners", "ci_runners", column: "runner_id", name: "fk_02de2ded36", on_delete: :nullify
   add_foreign_key "clusters_applications_runners", "clusters", on_delete: :cascade
   add_foreign_key "container_repositories", "projects"