Swap FK vulnerability_statistics to ci_pipelines for LFK

Swaps FK for vulnerability_statistics.latest_pipeline_id to ci_pipelines

Changelog: changed

db/post_migrate/20220119201340_remove_ci_pipelines_vulnerability_statistics_latest_pipeline_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveCiPipelinesVulnerabilityStatisticsLatestPipelineIdFk < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      execute('LOCK ci_pipelines, vulnerability_statistics IN ACCESS EXCLUSIVE MODE')
+
+      remove_foreign_key_if_exists(:vulnerability_statistics, :ci_pipelines, name: "fk_e8b13c928f")
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:vulnerability_statistics, :ci_pipelines, name: "fk_e8b13c928f", column: :latest_pipeline_id, target_column: :id, on_delete: :nullify)
+  end
+end

db/schema_migrations/20220119201340

+62b35cc5bd0abc5b7bcf4347346de832bbbed723fee7860ec649185d4d5fb53c
\ No newline at end of file

db/structure.sql

@@ -29926,9 +29926,6 @@ ALTER TABLE ONLY sprints
 ALTER TABLE ONLY application_settings
     ADD CONSTRAINT fk_e8a145f3a7 FOREIGN KEY (instance_administrators_group_id) REFERENCES namespaces(id) ON DELETE SET NULL;
 
-ALTER TABLE ONLY vulnerability_statistics
-    ADD CONSTRAINT fk_e8b13c928f FOREIGN KEY (latest_pipeline_id) REFERENCES ci_pipelines(id) ON DELETE SET NULL;
-
 ALTER TABLE ONLY integrations
     ADD CONSTRAINT fk_e8fe908a34 FOREIGN KEY (group_id) REFERENCES namespaces(id) ON DELETE CASCADE;
 

ee/spec/models/vulnerabilities/statistic_spec.rb

@@ -118,4 +118,11 @@ RSpec.describe Vulnerabilities::Statistic do
       end
     end
   end
+
+  context 'loose foreign key on vulnerability_statistics.latest_pipeline_id' do
+    it_behaves_like 'cleanup by a loose foreign key' do
+      let!(:parent) { create(:ci_pipeline) }
+      let!(:model) { create(:vulnerability_statistic, pipeline: parent) }
+    end
+  end
 end

spec/lib/gitlab/database/no_cross_db_foreign_keys_spec.rb

@@ -44,7 +44,6 @@ RSpec.describe 'cross-database foreign keys' do
       dast_site_profiles_pipelines.ci_pipeline_id
       external_pull_requests.project_id
       vulnerability_feedback.pipeline_id
-      vulnerability_statistics.latest_pipeline_id
     ).freeze
   end