Drupal 8: Batched hook_post_update_NAME() and hook_update_N() example

README.md

Example of batched update some entities with hook_post_update_NAME() or hook_update_N().

mymodule.post_update.php

<?php

/**
 * @file
 * Post update functions for the MYMODULE module.
 */

/**
 * Summary description for an update.
 */
function mymodule_post_update_NAME(array &$sandbox) {
  /** @var \Drupal\node\NodeStorageInterface $node_storage */
  $node_storage = \Drupal::entityTypeManager()->getStorage('node');

  // Fetching amount of data we need to process.
  // Runs only once per update.
  if (!isset($sandbox['total'])) {
    // This is the example of fetching amount of nodes of 'product' type.
    $result_count = $node_storage
      ->getQuery()
      ->condition('type', 'product')
      ->count()
      ->execute();

    // Write total of entities need to be processed to $sandbox.
    $sandbox['total'] = $result_count;
    // Initiate default value for current processing № of element.
    $sandbox['current'] = 0;
  }

  // Do not continue if no entities are found.
  if (empty($sandbox['total'])) {
    $sandbox['#finished'] = 1;
    return t('No products to be processed.');
  }

  // How much entities can be processed per batch.
  $limit = 50;
  // Fetching node id's for processing in current batch run. Make sure you are
  // query the same conditions as count query.
  $node_ids = $node_storage
    ->getQuery()
    ->condition('type', 'product')
    ->range($sandbox['current'], $limit)
    ->execute();
  // Load entities.
  $nodes = $node_storage->loadMultiple($node_ids);

  /** @var \Drupal\node\NodeInterface $node */
  foreach ($nodes as $node) {
    // Do something to with node.
    // And don't forget to save!
    $node->save();

    // Increment currently processed entities.
    $sandbox['current']++;
  }

  // The batch will finish when '#finished' will become '1'.
  $sandbox['#finished'] = ($sandbox['current'] / $sandbox['total']);

  // Print some progress.
  return t('@count products processed.', ['@count' => $sandbox['current']]);
}