Implements hook_field_storage_delete().
This function deletes data for all fields for an entity from the database.
function field_sql_storage_field_storage_delete($entity_type, $entity, $fields) {
foreach (field_info_instances($entity_type, $entity
->bundle()) as $instance) {
if (isset($fields[$instance['field_id']])) {
$field = field_info_field_by_id($instance['field_id']);
field_sql_storage_field_storage_purge($entity_type, $entity, $field, $instance);
}
}
}