Redmine

    user_custom_field_ids = CustomField.where(field_format: 'user').pluck(:id)

    if user_custom_field_ids.any?

      CustomValue.where(custom_field_id: user_custom_field_ids, value: self.id.to_s).delete_all

    end

class RemoveOrphanedUserCustomValues < ActiveRecord::Migration[5.2]

  def up

    user_custom_field_ids = CustomField.where(field_format: 'user').pluck(:id)

    if user_custom_field_ids.any?

      user_ids = Principal.pluck(:id)

      CustomValue.

        where(custom_field_id: user_custom_field_ids).

        where.not(value: [nil, ''] + user_ids).

        delete_all

    end

  end

end

  def test_remove_custom_field_references_upon_destroy

    cf1 = IssueCustomField.create(field_format: 'user', name: 'user cf', is_for_all: true, tracker_ids: Tracker.pluck(:id))

    cf2 = IssueCustomField.create(field_format: 'user', name: 'users cf', is_for_all: true, multiple: true, tracker_ids: Tracker.pluck(:id))

    issue = Issue.first

    issue.init_journal(@admin)

    assert_difference ->{cf1.custom_values.count} do

      assert_difference ->{cf2.custom_values.count}, 2 do

        issue.update_attributes(custom_field_values: {

          cf1.id => @jsmith.id,

          cf2.id => [@dlopper.id, @jsmith.id]

        })

      end

    end

    assert cv1 = cf1.custom_values.where(customized_id: issue.id).last

    assert_equal @jsmith.id.to_s, cv1.value

    assert cv2 = cf2.custom_values.where(customized_id: issue.id)

    assert_equal 2, cv2.size

    assert cv2a = cv2.detect{|cv|cv.value == @dlopper.id.to_s}

    assert cv2b = cv2.detect{|cv|cv.value == @jsmith.id.to_s}

    assert_difference ->{CustomValue.count}, -2 do

      @jsmith.destroy

    end

    assert_raise(ActiveRecord::RecordNotFound){cv1.reload}

    assert_raise(ActiveRecord::RecordNotFound){cv2b.reload}

    cv2a.reload

    assert_equal @dlopper.id.to_s, cv2a.value

  end