How to prevent a field with thousands of files from loading on Edit operation?

Question

I have a process running that renders a PDF to PNGs and attaches those PNGs to a file field. There is one PDF's results per node, but there we have a bunch of PDFs with 10,000+ pages. We've found that this results in the operation of loading an edit form to eat quite a lot of memory (a node with 12,000 attached files ate up all 4GB of RAM on our server before Apache killed the process for taking up too much memory).

Does anyone have any ideas how we might prevent the field from loading? It looks like I could hack file_field_load() to not perform its task given the user is on an edit page and the troubled field is expected but it would be cool if there was a solution that wasn't a hack.

The stack trace when the troubled field is set to not display is:

 1. {main}()  /index.php:0
 2. menu_execute_active_handler()  /index.php:18
 3. call_user_func_array()  /includes/menu.inc:348
 4. node_page_edit()  /includes/menu.inc:0
 5. drupal_get_form()  /modules/node/node.pages.inc:15
 6. drupal_process_form()  /includes/form.inc:121
 7. form_builder()  /includes/form.inc:406
 8. form_builder()  /includes/form.inc:930
 9. form_builder()  /includes/form.inc:930
10. _form_builder_handle_input_element()  /includes/form.inc:889
11. imagefield_widget_value()  /includes/form.inc:1020
12. filefield_widget_value()  /sites/all/modules/contrib/imagefield/imagefield_widget.inc:207
13. field_file_load()  /sites/all/modules/contrib/filefield/filefield_widget.inc:215
14. _field_file_cache()  /sites/all/modules/contrib/filefield/field_file.inc:51

And when the field is set to display:

1. {main}()    /index.php:0
2. menu_execute_active_handler()    /index.php:18
3. call_user_func_array()    /includes/menu.inc:348
4. node_page_edit()    /includes/menu.inc:0
5. drupal_get_form()    /modules/node/node.pages.inc:15
6. drupal_process_form()    /includes/form.inc:121
7. form_builder()    /includes/form.inc:406
8. form_builder()    /includes/form.inc:930
9. form_builder()    /includes/form.inc:930
10. form_builder()    /includes/form.inc:930
11. _form_builder_handle_input_element()    /includes/form.inc:889
12. process_weight()    /includes/form.inc:1063

Answer 1

Would it be enough to deny editing rights to that field using Content Permissions?

Answer 2

Per my comment, use hook_nodeapi() when $op == 'load' as a place to unset() that field to prevent it from being built in the form code.

Answer 3

You could try to hook_form_alter the edit form for that content type, but I am not sure it will happen too late in the process.

This post can provide guidance: https://stackoverflow.com/questions/1067782/drupal-form-alter

It would essentially start out as

function module_form_alter (&$form, &$form_state, $form_id)
{
  if (isset($form['#node']) && $form_id == $form['#node']->type .'_node_form') {
  }
}

You would need to add logic to check for your content type, and then unset the necessary elements.

I am not 100% sure if it will leave the fields as-is when you do this, though, so test first on a safe copy of your site.