为什么我的程序会出现这样的错误?

Traceback (most recent call last):
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 511, in __call__
handler.get(*groups)
File "/base/data/home/apps/v2ping/1.345793633376194920/member.py", line 68, in get
for reply in q3:
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 1786, in __iter__
return self.run()
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 2365, in run
**kwargs))
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 1849, in fetch
raw = raw_query.Get(limit, offset, rpc=rpc)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 1269, in Get
limit=limit, offset=offset, prefetch_count=limit, **kwargs)._Get(limit)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 1178, in _Run
rpc=rpc)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 1211, in _RunInternal
str(exc) + '\nThis query needs this index:\n' + yaml)
NeedIndexError: no matching index found.
This query needs this index:
- kind: Reply
properties:
- name: member_num
- name: created
direction: desc