Bulkload with correctly unindexed properties: http://alex.cloudware.it/2012/08/unindexed-entity-properties-with-bulk.html

bulkloader.yaml

python_preamble:
- import: base64
- import: re
- import: google.appengine.ext.bulkload.transform
- import: google.appengine.ext.bulkload.bulkloader_wizard
- import: google.appengine.ext.db
- import: google.appengine.api.datastore
- import: google.appengine.api.users
- import: postimport

transformers:
- kind: MyModel
  connector: simplexml
  connector_options:
    xpath_to_nodes: /whatever
    style: element_centric
  post_import_function: postimport.unindex_properties
  property_map:
    - ...props definitions...

postimport.py

from google.appengine.api import datastore

_UNINDEXED_PROPS = {
  'MyModel': ['prop1', 'prop2', 'prop3'],
  'MyOtherModel': ['some_prop']
}

def unindex_properties(input_dict, entity, bulkload_state_copy):
  """
  Runs on after every entity import and sets correct unindexed properties.
  """
  if isinstance(entity, datastore.Entity):
    kind = entity.kind()
    if kind in _UNINDEXED_PROPS:
      props = _UNINDEXED_PROPS[kind]
      entity.set_unindexed_properties(props)
  return entity