Errors while loading data from Google App Engine using bootloader

I am trying to load some data from a data warehouse using the following command:

appcfg.py download_data --config_file=bulkloader.yaml --application=myappname 
                        --kind=mykindname --filename=myappname_mykindname.csv
                        --url=http://myappname.appspot.com/_ah/remote_api 

When I didn’t have a lot of data in this particular view / table, I could load the data with one shot - from time to time the following error:

.................................[ERROR   ] [Thread-11]
ExportProgressThread:
Traceback (most recent call last):
  File "C:\Program Files\Google\google_appengine\google\appengine\tools
\bulkload
er.py", line 1448, in run
    self.PerformWork()
  File "C:\Program Files\Google\google_appengine\google\appengine\tools
\bulkload
er.py", line 2216, in PerformWork
    item.key_end)
  File "C:\Program Files\Google\google_appengine\google\appengine\tools
\bulkload
er.py", line 2011, in StoreKeys
    (STATE_READ, unicode(kind), unicode(key_start), unicode(key_end)))
OperationalError: unable to open database file

This is what I see in the server log:

Traceback (most recent call last):
  File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/remote_api/handler.py", line 277, in post
    response_data = self.ExecuteRequest(request)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/remote_api/handler.py", line 308, in ExecuteRequest
    response_data)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/
api/apiproxy_stub_map.py", line 86, in MakeSyncCall
    return stubmap.MakeSyncCall(service, call, request, response)
  File "/base/python_runtime/python_lib/versions/1/google/appengine/
api/apiproxy_stub_map.py", line 286, in MakeSyncCall
    rpc.CheckSuccess()
  File "/base/python_runtime/python_lib/versions/1/google/appengine/
api/apiproxy_rpc.py", line 126, in CheckSuccess
    raise self.exception
ApplicationError: ApplicationError: 4 no matching index found. 

When such an error occurred, I would just restart the download and things would work well.

, . , ~ 3500 5 - . ? script, - , .

, , - .

. ( App Engine). , , , , . , :

[INFO    ] Have 3220 entities, 3220 previously transferred
[INFO    ] 3220 entities (1003 bytes) transferred in 2.9 seconds

, ~ 4300 . ?

!