Drupal 8 - Programmatically find custom canonical urls and set default

Drupal 8 - Programmatically update canonical urls

$query = \Drupal::entityQuery('node');

$node_ids = $query
   ->condition('status', 1)
   ->exists('field_meta_tags')
   ->execute();

$count = 0;

foreach($node_ids as $node_id) {
  $node = \Drupal\node\Entity\Node::load($node_id);
  $metatag = unserialize($node->get('field_meta_tags')->value);

  if (strpos($node->get('field_meta_tags')->value,'canonical') > -1) {
    print_r('<a href="https://mysite.com/node/'.$node_id.'/edit" target="_blank">https://mysite.com/node/'.$node_id.'/edit</a>'); echo '<br />';
    print_r($metatag['canonical_url']); echo '<br /><br />';
    unset($metatag['canonical_url']);
    $node->set('field_meta_tags', serialize($metatag));
    $node->save();
    $count++;    
  }
}

print_r('Fixed: '.$count);