On a site that heavily uses Drupal core's taxonomy, we are encountering serious problems when editing content: Already entered taxonomy terms are not properly loaded into the node editing form; fields that should contain values are rendered empty; when the nodes are saved, the terms are lost. So this is not a display issue.
Please note: Some terms are not loaded into the node editing form. We know exactly which terms should be there because a View displays the terms in a structured fashion.
I am aware that Drupal inherits multiple issues with large forms from PHP; for example, large user permission screens are not being saved in Drupal, because PHP has a default value for 'max_input_vars' of '1000'; by increasing this value, e.g. to '1500', Drupal becomes able to save user permissions again. We'Re supecting something similar with the node editing screens. However, in our case, values are not even inserted from the database into the node editing form, so it's totally unclear where to even start looking for a solution.
- Drupal 6 (Pressflow)
- Around 110,000 nodes
- 24 vocabularies with > 100,000 terms
Also noteworthy: The problem with incomplete node editing forms is not limited to taxonomy terms; it sporadically also applies to other form elements like attach images.
Are there any PHP configuration values that could cause this misbehaviour or does Form API have any hard limits in redard not the size of node editing forms (e.g. number of form elements per form, memory limits per node editing form)?