Drupal 6: Updating nodes when changing CCK field allowed value list using a submit handler

In this article I’ll address an issue that has surfaced on every recent project I’ve been working on: how to update nodes when a CCK field’s allowed values list changes. For my projects, I implemented a variety of batch processes and drush scripts to solve this problem. But for this article, I decided to implement a form submit handler solution to automatically update nodes when the CCK field settings page is submitted. Please be careful when implementing code like this, it has potential to update a lot of nodes, and hit memory limitation issues depending on how many nodes need to be updated. As I mentioned before, I implemented a combination of batch APIs and drush scripts to process production environments; I implemented this code in a development environment. Anyway..

I created a new content type “band”, and added a CCK text/select field (genre) with an allowed values list:

I used Devel’s auto-generate content functionality to create 20 nodes (/admin/generate/content), and then added a simple view to show the node’s title and genre:

Now that I had some working test data, I added some code to a custom module to modify the CCK field property settings page, and add a submit handler update the nodes:

<?php

// define module constants
define('CCK_FIELD_PROCESS', 'field_genre');
define('CCK_TYPE_PROCESS', 'band');

/**
 * Implements hook_form_alter()
 */
function helper_form_alter(&$form, &$form_state, $form_id) {

  // check for CCK form, CCK type, and CCK field (see above constants)
  if ($form_id == 'content_field_edit_form' && $form['type_name']['#value'] == CCK_TYPE_PROCESS && $form['field_name']['#value'] == CCK_FIELD_PROCESS) {

    // get original allowed values
    $original_allowed_values_string = $form['field']['allowed_values_fieldset']['allowed_values']['#default_value'];

    // explode values, get array of values
    $exploded = explode("\n", $original_allowed_values_string);
    $original_allowed_values_array = array();
    foreach ($exploded as $data) {

      // explode data on "|"
      list($key, $value) = $exploded2 = explode('|', $data);
      $original_allowed_values_array[$key] = $value;

    }

    // ensure data exists
    if (empty($original_allowed_values_array)) {
      return;
    }

    // store original values in form state storage
    $form_state['storage']['original_allowed_values'] = $original_allowed_values_array;

    // store other information in form state
    $form_state['storage']['cck_type'] = CCK_TYPE_PROCESS;
    $form_state['storage']['cck_field'] = CCK_FIELD_PROCESS;

    // add submit handler
    $form['#submit'][] = '_helper_form_alter_content_field_edit_form_submit';

  }

}

/**
 * Implements custom form submit handler
 */
function _helper_form_alter_content_field_edit_form_submit($form, &$form_state) {

  // get new allowed values list
  $new_allowed_values_string = $form_state['values']['allowed_values'];

  // ensure data exists
  if (empty($new_allowed_values_string)) {
    return;
  }

  // explode values, get array of values
  $exploded = explode("\n", $new_allowed_values_string);
  $new_allowed_values_array = array();
  foreach ($exploded as $data) {

    // explode data on "|"
    list($key, $value) = $exploded2 = explode('|', $data);
    $new_allowed_values_array[$key] = $value;

  }

  // ensure data exists
  if (empty($new_allowed_values_array)) {
    return;
  }

  // NOTE: the next few lines gets the key values from the allowed values
  // and checks to see which are different.
  // This code assumes any change to the keys (including changing the order) will update the nodes.
  // Update to your heart's content
  $new_keys = array_keys($new_allowed_values_array);
  $old_keys = array_keys($form_state['storage']['original_allowed_values']);

  $key_diffs = array();
  foreach ($old_keys as $key => $value) {

    if ($new_keys[$key] != $value) {
      $key_diffs[$value] = $new_keys[$key];
    }

  }

  // ensure data has changed
  if (empty($key_diffs)) {
    unset($form_state['storage']);
    return;
  }

  // get data from form storage
  $cck_field = $form_state['storage']['cck_field'];
  $cck_type = $form_state['storage']['cck_type'];

  // loop through key diffs
  foreach ($key_diffs as $old => $new) {

    // get a list of node ids that need to be updated
    // NOTE: this sql assumes the field is NOT shared
    $sql = "
      select n.nid
      from {node} n
      join {content_type_%s} b on b.nid = n.nid and b.vid = n.vid
      where n.type = '%s' and b.%s_value = '%s'
    ";
    $resource = db_query($sql, $cck_type, $cck_type, $cck_field, $old);
    $node_ids = array();
    while ($row = db_fetch_object($resource)) {
      $node_ids[] = $row->nid;
    }

    // ensure results exist
    if (empty($node_ids)) {
      continue;
    }

    // loop through node ids
    // NOTE: got a lot of nodes? you might need a batch API instead
    foreach ($node_ids as $nid) {

      // load node
      $node = node_load($nid, NULL, TRUE);

      // ensure node loaded
      if (!is_object($node)) {
        continue;
      }

      // update node properties
      $node->{$cck_field}[0]['value'] = $new;
      $node->revision = TRUE;
      node_save($node);

      // remove cck cache for node
      db_query("DELETE FROM {cache_content} WHERE cid LIKE 'content:%d%'", $node->nid);

    }

  }

  // remove form storage
  unset($form_state['storage']);

}
?>

To test this code, I went back to the CCK field settings page (example: /admin/content/node-type/band/fields/field_genre), updated the allowed value list, and saved.

The form submit handler is triggered and the nodes are updated. Refreshing my view shows the updated genre fields on my test nodes: