gistfile1.txt

class Nodes extends SqlBase {

  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this->select('node', 'n')
      ->fields('n', ['nid']);
    // Add the value for the custom id.
    $query->addExpression(':now', 'current__date', [':now' => date('Ymd')]);
    return $query;
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    return [
      'nid' => [
        'type' => 'string',
      ],
      'current__date' => [
        'type' => 'string',
        'max_length' => '10',
      ],
    ];
  }

You must use the above plugin with ignore_map configured on it.