1 files changed, 38 insertions, 0 deletions
diff --git a/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb b/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb
new file mode 100644
index 00000000000..e6a780d0964
--- /dev/null
+++ b/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb
@@ -0,0 +1,38 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class IssuesMilestoneIdForeignKey < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  class Issue < ActiveRecord::Base
+    include EachBatch
+
+    self.table_name = 'issues'
+
+    def self.with_orphaned_milestones
+      where('NOT EXISTS (SELECT true FROM milestones WHERE milestones.id = issues.milestone_id)')
+    end
+  end
+
+  def up
+    Issue.with_orphaned_milestones.each_batch(of: 100) do |batch|
+      batch.update_all(milestone_id: nil)
+    end
+
+    add_concurrent_foreign_key(
+      :issues,
+      :milestones,
+      column: :milestone_id,
+      on_delete: :nullify
+    )
+  end
+
+  def down
+    remove_foreign_key_without_error(:issues, column: :milestone_id)
+  end
+end