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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: 2.4, 2.4.1
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Component/s: None
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When subscript notation is used on a cursor object to get a specific document from the cursor a clone of the original cursor is made. Changes to clone in 2.4 break operations that require an ordered dictionary. The best example is when using $hint:
>>> import pymongo
>>> c = pymongo.MongoClient()
>>> hint = [(u'uid', 1), (u'service', 1), (u'site_path', 1), (u'url_path', 1), (u'status', 1)]
>>> cur = c.test.post.find( { "site_path": "/ued/", "status": "public", "url_path": "thinking/wo-wei-shi-yao-tao-yanpm", "uid": 4919465, "service": "dropbox" }).hint(hint)
>>> cur.next()
{u'site_path': u'/ued/', u'status': u'public', u'url_path': u'thinking/wo-wei-shi-yao-tao-yanpm', u'uid': 4919465.0, u'service': u'dropbox', u'_id': ObjectId('50e87075deaf17f2dc7632cb')}
>>> cur = c.test.post.find( { "site_path": "/ued/", "status": "public", "url_path": "thinking/wo-wei-shi-yao-tao-yanpm", "uid": 4919465, "service": "dropbox" }).hint(hint)
>>> cur[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "pymongo/cursor.py", line 470, in __getitem__
for doc in clone:
File "pymongo/cursor.py", line 814, in next
if len(self.__data) or self._refresh():
File "pymongo/cursor.py", line 763, in _refresh
self.__uuid_subtype))
File "pymongo/cursor.py", line 720, in __send_message
self.__uuid_subtype)
File "pymongo/helpers.py", line 105, in _unpack_response
error_object["$err"])
pymongo.errors.OperationFailure: database error: bad hint
Notice the second operation does cur[0] instead of cur.next(), creating a clone of the original cursor. The clone operation seems to replace the SON instance with a regular dictionary, changing the index hint order:
>>> cur = c.test.post.find( { "site_path": "/ued/", "status": "public", "url_path": "thinking/wo-wei-shi-yao-tao-yanpm", "uid": 4919465, "service": "dropbox" }).hint(hint)
>>>
>>> cur._Cursor__hint
SON([(u'uid', 1), (u'service', 1), (u'site_path', 1), (u'url_path', 1), (u'status', 1)])
>>>
>>> cln = cur._Cursor__clone()
>>> cln._Cursor__hint
{u'site_path': 1, u'status': 1, u'url_path': 1, u'uid': 1, u'service': 1}
- related to
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- Closed
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