<?php

use Drupal\node\Entity\Node;
 
/**
* Implements hook_update_N().
*
* Set default value to new field field_registered on all Person nodes.
*/
function MY_MODULE_update_8001(&$sandbox) {
  // Initialize some variables during the first pass through.
  if (!isset($sandbox['total'])) {
    $nids = \Drupal::entityQuery('node')
      ->condition('type', 'person')
      ->execute();
    $sandbox['total'] = count($nids);
    $sandbox['current'] = 0;
  }
 
  $nodes_per_batch = 25;
 
  // Handle one pass through.
  $nids = \Drupal::entityQuery('node')
    ->condition('type', 'person')
    ->range($sandbox['current'], $nodes_per_batch)
    ->execute();
 
  foreach($nids as $nid) {
    $node = Node::load($nid);
    $node->field_board_member->value = 0;
    $node->save();
    $sandbox['current']++;
  }
 
  drupal_set_message($sandbox['current'] . ' nodes processed.');
 
  if ($sandbox['total'] == 0) {
    $sandbox['#finished'] = 1;
  } else {
    $sandbox['#finished'] = ($sandbox['current'] / $sandbox['total']);
  }
 
}