Retain timelogs for deleted notes

changelogs/unreleased/retain-timelogs-for-deleted-notes.yml

+---
+title: Prevent loss of timelogs when deleting notes
+merge_request: 58525
+author: Lee Tickett @leetickett
+type: fixed

db/post_migrate/20210403022952_remove_notes_delete_cascade_timelogs.rb

+# frozen_string_literal: true
+
+class RemoveNotesDeleteCascadeTimelogs < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  CONSTRAINT_NAME = 'fk_timelogs_note_id'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :timelogs, :notes, column: :note_id, on_delete: :nullify, name: CONSTRAINT_NAME
+
+    with_lock_retries do
+      remove_foreign_key_if_exists :timelogs, :notes, column: :note_id, on_delete: :cascade
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key :timelogs, :notes, column: :note_id, on_delete: :cascade
+
+    with_lock_retries do
+      remove_foreign_key_if_exists :timelogs, :notes, column: :note_id, on_delete: :nullify, name: CONSTRAINT_NAME
+    end
+  end
+end

db/schema_migrations/20210403022952

+c62c2e13bdad42cc1f112f9854fe8d25e1e2aa082cb28341a661c93b8587f1f8
\ No newline at end of file

db/structure.sql

@@ -25028,9 +25028,6 @@ ALTER TABLE ONLY issues
 ALTER TABLE ONLY protected_branch_merge_access_levels
     ADD CONSTRAINT fk_8a3072ccb3 FOREIGN KEY (protected_branch_id) REFERENCES protected_branches(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY timelogs
-    ADD CONSTRAINT fk_8d058cd571 FOREIGN KEY (note_id) REFERENCES notes(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY releases
     ADD CONSTRAINT fk_8e4456f90f FOREIGN KEY (author_id) REFERENCES users(id) ON DELETE SET NULL;
 
@@ -26885,6 +26882,9 @@ ALTER TABLE ONLY timelogs
 ALTER TABLE ONLY timelogs
     ADD CONSTRAINT fk_timelogs_merge_requests_merge_request_id FOREIGN KEY (merge_request_id) REFERENCES merge_requests(id) ON DELETE CASCADE;
 
+ALTER TABLE ONLY timelogs
+    ADD CONSTRAINT fk_timelogs_note_id FOREIGN KEY (note_id) REFERENCES notes(id) ON DELETE SET NULL;
+
 ALTER TABLE ONLY u2f_registrations
     ADD CONSTRAINT fk_u2f_registrations_user_id FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;