Index: modules/field/field.api.php
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/field.api.php,v
retrieving revision 1.74
diff -u -r1.74 field.api.php
--- modules/field/field.api.php	22 Apr 2010 23:38:17 -0000	1.74
+++ modules/field/field.api.php	23 Apr 2010 11:02:05 -0000
@@ -1050,6 +1050,33 @@
 }
 
 /**
+ * Act on field_purge_data.
+ *
+ * This hook is invoked in field_purge_data() and allows modules to act on
+ * purging data from a single field pseudo-entity.  For example, if a module
+ * relates data in the field with its own data, it may purge its own data
+ * during this process as well.
+ *
+ * @param $entity_type
+ *   The type of $entity; e.g. 'node' or 'user'.
+ * @param $entity
+ *   The pseudo-entity whose field data is being purged.
+ * @param $field
+ *   The (possibly deleted) field whose data is being purged.
+ * @param $instance
+ *   The deleted field instance whose data is being purged.
+ *
+ * @see @link field_purge Field API bulk data deletion @endlink
+ * @see field_purge_data()
+ */
+function hook_field_attach_purge($entity_type, $entity, $field, $instance) {
+  // find the corresponding data in mymodule and purge it
+  if($entity_type == 'node' && $field->field_name == 'my_field_name') {
+    mymodule_remove_mydata($entity->nid);
+  }
+}
+
+/**
  * Act on field_attach_view.
  *
  * This hook is invoked after the field module has performed the operation.
Index: modules/field/field.crud.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/field.crud.inc,v
retrieving revision 1.56
diff -u -r1.56 field.crud.inc
--- modules/field/field.crud.inc	22 Apr 2010 19:06:34 -0000	1.56
+++ modules/field/field.crud.inc	23 Apr 2010 11:02:06 -0000
@@ -1040,7 +1040,7 @@
  * @param $entity_type
  *   The type of $entity; e.g. 'node' or 'user'.
  * @param $entity
- *   The pseudo-entity whose field data to delete.
+ *   The pseudo-entity whose field data is being purged.
  * @param $field
  *   The (possibly deleted) field whose data is being purged.
  * @param $instance