/**
 * Implements hook_field_purge_field_storage().
 */
function {{ machine_name }}_field_purge_field_storage(\Drupal\field\Entity\FieldStorageConfig $field_storage) {
  \Drupal::database()->delete('my_module_field_storage_info')
    ->condition('uuid', $field_storage->uuid())
    ->execute();
}
