Change constraint on foreign key from cascade to nullify

Add changelog entry

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Remove rubocop offence

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changelogs/unreleased/recreate_foreign_key_with_nullify.yml

+---
+title: Recreate foreign key in project settings to use nullify instead of cascade
+merge_request: 29767
+author:
+type: changed

db/migrate/20200417075843_remove_and_add_foreign_key_to_project_settings.rb

+# frozen_string_literal: true
+
+class RemoveAndAddForeignKeyToProjectSettings < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  CONSTRAINT_NAME = 'fk_project_settings_push_rule_id'
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :project_settings, :push_rules, column: :push_rule_id, name: CONSTRAINT_NAME, on_delete: :nullify
+    remove_foreign_key_if_exists :project_settings, column: :push_rule_id, on_delete: :cascade
+  end
+
+  def down
+    add_concurrent_foreign_key :project_settings, :push_rules, column: :push_rule_id, on_delete: :cascade
+    remove_foreign_key_if_exists :project_settings, column: :push_rule_id, name: CONSTRAINT_NAME, on_delete: :nullify
+  end
+end

db/structure.sql

@@ -10901,9 +10901,6 @@ ALTER TABLE ONLY public.epics
 ALTER TABLE ONLY public.ci_pipelines
     ADD CONSTRAINT fk_3d34ab2e06 FOREIGN KEY (pipeline_schedule_id) REFERENCES public.ci_pipeline_schedules(id) ON DELETE SET NULL;
 
-ALTER TABLE ONLY public.project_settings
-    ADD CONSTRAINT fk_413a953e20 FOREIGN KEY (push_rule_id) REFERENCES public.push_rules(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY public.ci_pipeline_schedule_variables
     ADD CONSTRAINT fk_41c35fda51 FOREIGN KEY (pipeline_schedule_id) REFERENCES public.ci_pipeline_schedules(id) ON DELETE CASCADE;
 
@@ -11327,6 +11324,9 @@ ALTER TABLE ONLY public.path_locks
 ALTER TABLE ONLY public.personal_access_tokens
     ADD CONSTRAINT fk_personal_access_tokens_user_id FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE;
 
+ALTER TABLE ONLY public.project_settings
+    ADD CONSTRAINT fk_project_settings_push_rule_id FOREIGN KEY (push_rule_id) REFERENCES public.push_rules(id) ON DELETE SET NULL;
+
 ALTER TABLE ONLY public.protected_branch_merge_access_levels
     ADD CONSTRAINT fk_protected_branch_merge_access_levels_user_id FOREIGN KEY (user_id) REFERENCES public.users(id) ON DELETE CASCADE;
 
@@ -13512,6 +13512,7 @@ COPY "schema_migrations" (version) FROM STDIN;
 20200416120128
 20200416120354
 20200417044453
+20200417075843
 20200417145946
 20200420104303
 20200420104323