Sort operation used more than the maximum 33554432 bytes of RAM

[bodqhrohro]

I encountered this when exporting a large chat (137988 messages):

Traceback (most recent call last):
  File "/media/d/temp/git/matrix-archive/export_messages.py", line 80, in <module>
    export_archive()
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/media/d/temp/git/matrix-archive/export_messages.py", line 66, in export_archive
    print(f"Writing {len(messages)} messages to {filename!r}")
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/mongoengine/queryset/queryset.py", line 62, in __len__
    list(self._iter_results())
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/mongoengine/queryset/queryset.py", line 110, in _iter_results
    self._populate_cache()
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/mongoengine/queryset/queryset.py", line 129, in _populate_cache
    self._result_cache.append(next(self))
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/mongoengine/queryset/base.py", line 1619, in __next__
    raw_doc = next(self._cursor)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/cursor.py", line 1207, in next
    if len(self.__data) or self._refresh():
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/cursor.py", line 1124, in _refresh
    self.__send_message(q)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/cursor.py", line 999, in __send_message
    response = client._run_operation_with_response(
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1368, in _run_operation_with_response
    return self._retryable_read(
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1471, in _retryable_read
    return func(session, server, sock_info, slave_ok)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/mongo_client.py", line 1360, in _cmd
    return server.run_operation_with_response(
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/server.py", line 135, in run_operation_with_response
    _check_command_response(first, sock_info.max_wire_version)
  File "/home/bodqhrohro/.local/lib/python3.8/site-packages/pymongo/helpers.py", line 160, in _check_command_response
    raise OperationFailure(errmsg, code, response, max_wire_version)
pymongo.errors.OperationFailure: Executor error during find command :: caused by :: Sort operation used more than the maximum 33554432 bytes of RAM. Add an index, or specify a smaller limit., full error: {'ok': 0.0, 'errmsg': 'Executor error during find command :: caused by :: Sort operation used more than the maximum 33554432 bytes of RAM. Add an index, or specify a smaller limit.', 'code': 96, 'codeName': 'OperationFailed'}

This can be worked around, though adding an actual index should be better.