Example of batch function to delete nodes

drupal7 batch example

/**
 * Callback function for delete all nodes.
 *
 * @param array $types_of_content
 *   Array of machine node type names to delete.
 *
 * @param array $except_uids
 *   Array with uids of ingnore users who created nodes.
 */
function _delete_all_nodes($types_of_content, $except_uids = array()) {

  if (empty($types_of_content)) {
    drush_print('Node types not specified.');
    return;
  }

  $results = db_select('node', 'n')
    ->fields('n', array('nid'))
    ->condition('n.type', $types_of_content, 'IN');

  // Exclude nodes created from special users.
  if (!empty($except_uids)) {
    $results = $results->condition('n.uid', $except_uids, 'NOT IN');
  }

  $results = $results->orderBy('n.nid', 'ASC')
    ->execute();
  $nids = $results->fetchCol();
  $num_of_nodes = count($nids);

  if ($num_of_nodes < 1) {
    drush_print('Not have nodes for delete.');
    return;
  }

  $chunks = array_chunk($nids, 20);
  $operations = array();
  $progress = 0;
  $limit = 20;
  $max = $num_of_nodes;

  // Set up our batch operations.
  foreach ($chunks as $chunk) {
    $operations[] = array(
      '_delete_nodes',
      array(
        $chunk, $progress, $limit, $max,
      ),
    );
    $progress = $progress + $limit;
  }

  $batch = array(
    'operations' => $operations,
    'title' => t('Delete nodes'),
    'init_message' => t('Initializing'),
    'error_message' => t('An error occurred'),
    'progress_message' => t('Processed batch #@current out of @total.'),
    'finished' => '_common_delete_nodes_finished',
  );
  // Get the batch process all ready!
  batch_set($batch);
  $batch =& batch_get();

  // Because we are doing this on the back-end, we set progressive to false.
  $batch['progressive'] = FALSE;

  // Start processing the batch operations.
  drush_backend_batch_process();
}

/**
 * Callback function for delete all nodes batch process.
 */
function _delete_nodes($nids, $progress, $limit, $max, &$context) {
  // Set default starting values.
  if (empty($context['sandbox'])) {
    $context['sandbox'] = array();
    $context['sandbox']['progress'] = 0;
    $context['sandbox']['current_nid'] = 0;
    $context['sandbox']['max'] = $limit;
  }

  if (!empty($nids)) {
    node_delete_multiple($nids);

    foreach ($nids as $nid) {
      $path = path_load(
        array('source' => 'node/' . $nid)
      );
      path_delete($path['pid']);
    }
  }

  $context['results'][] = $max;
  $context['sandbox']['progress'] += $progress;
  $context['sandbox']['current_nid'] = array_pop($nids);

  // Inform the batch engine that we are not finished,
  // and provide an estimation of the completion level we reached.
  if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
    $context['finished'] = (($context['sandbox']['max'] - $context['sandbox']['progress']) <= $limit) || ($context['sandbox']['progress'] >= $context['sandbox']['max']);
  }
}

/**
 * Callback function for delete all nodes batch finish process.
 */
function _delete_nodes_finished($success, $results, $operations) {
  if ($success) {
    drupal_set_message(t('@count nodes was deleted.', array('@count' => array_pop($results))));
  }
  else {
    $error_operation = reset($operations);
    drupal_set_message(
      t('An error occurred while processing @operation with arguments : @args',
        array(
          '@operation' => $error_operation[0],
          '@args' => print_r($error_operation[0], TRUE),
        )
      )
    );
  }
}