<?php

/**
 * @file
 * Install, update, and uninstall functions for the batch_example module.
 */

/**
 * Example of batch-driven update function.
 *
 * Because some update functions may require the batch API, the $sandbox
 * provides a place to store state. When $sandbox['#finished'] == TRUE,
 * calls to this update function are completed.
 *
 * The $sandbox param provides a way to store data during multiple invocations.
 * When the $sandbox['#finished'] == 1, execution is complete.
 *
 * This dummy 'update' function changes no state in the system. It simply
 * loads each node.
 *
 * To make this update function run again and again, execute the query
 * "update system set schema_version = 0 where name = 'batch_example';"
 * and then run /update.php.
 *
 * @ingroup batch_example
 */
function batch_example_update_7100(&$sandbox) {
  $ret = array();

  // Use the sandbox at your convenience to store the information needed
  // to track progression between successive calls to the function.
  if (!isset($sandbox['progress'])) {
    // The count of nodes visited so far.
    $sandbox['progress'] = 0;
    // Total nodes that must be visited.
    $sandbox['max'] = db_query('SELECT COUNT(nid) FROM {node}')->fetchField();
    // A place to store messages during the run.
    $sandbox['messages'] = array();
    // Last node read via the query.
    $sandbox['current_node'] = -1;
  }

  // Process nodes by groups of 10 (arbitrary value).
  // When a group is processed, the batch update engine determines
  // whether it should continue processing in the same request or provide
  // progress feedback to the user and wait for the next request.
  $limit = 10;

  // Retrieve the next group of nids.
  $result = db_select('node', 'n')
    ->fields('n', array('nid'))
    ->orderBy('n.nid', 'ASC')
    ->where('n.nid > :nid', array(':nid' => $sandbox['current_node']))
    ->extend('PagerDefault')
    ->limit($limit)
    ->execute();
  foreach ($result as $row) {
    // Here we actually perform a dummy 'update' on the current node.
    $node = db_query('SELECT nid FROM {node} WHERE nid = :nid', array(':nid' => $row->nid))->fetchField();

    // Update our progress information.
    $sandbox['progress']++;
    $sandbox['current_node'] = $row->nid;
  }

  // Set the "finished" status, to tell batch engine whether this function
  // needs to run again. If you set a float, this will indicate the progress
  // of the batch so the progress bar will update.
  $sandbox['#finished'] = ($sandbox['progress'] >= $sandbox['max']) ? TRUE : ($sandbox['progress'] / $sandbox['max']);

  // Set up a per-run message; Make a copy of $sandbox so we can change it.
  // This is simply a debugging stanza to illustrate how to capture status
  // from each pass through hook_update_N().
  $sandbox_status = $sandbox;
  // Don't want them in the output.
  unset($sandbox_status['messages']);
  $sandbox['messages'][] = t('$sandbox=') . print_r($sandbox_status, TRUE);

  if ($sandbox['#finished']) {
    // hook_update_N() may optionally return a string which will be displayed
    // to the user.
    $final_message = '<ul><li>' . implode('</li><li>', $sandbox['messages']) . "</li></ul>";
    return t('The batch_example demonstration update did what it was supposed to do: @message', array('@message' => $final_message));
  }
}
