使用 pymongo 时有时会遇到提示如下的错误:
File "/usr/local/lib/python2.7/dist-packages/pymongo/cursor.py", line 1090, in next if len(self.__data) or self._refresh(): File "/usr/local/lib/python2.7/dist-packages/pymongo/cursor.py", line 1022, in _refresh self.__uuid_subtype)) File "/usr/local/lib/python2.7/dist-packages/pymongo/cursor.py", line 958, in __send_message self.__compile_re) File "/usr/local/lib/python2.7/dist-packages/pymongo/helpers.py", line 113, in _unpack_response error_object) OperationFailure: database error: Executor error: Overflow sort stage buffered data usage of 33597009 bytes exceeds internal limit of 33554432 bytes为什么会出现这样的错误呢？ 原来 mongodb 限制了在内存中进行 sort 操作（无法使用索引的情况下）时所使用的最大内存大小，默认是 32 M(33554432 bytes)。
如果要修改这个限制的话，可以通过如下的 mongo 命令进行修改，比如修改为 50 M(52428800 bytes):
> use admin > db.adminCommand({setParameter: 1, internalQueryExecMaxBlockingSortBytes: 52428800}) 参考资料 mongodb - How to increase buffered data limit? - Ask Ubuntu MongoDB Limits and Thresholds ― MongoDB Manual 3.2