PYTHON-1529 - No implicit sessions with parallel_scan

Author: behackett

pymongo/collection.py

@@ -1493,16 +1493,24 @@ def parallel_scan(self, num_cursors, session=None, **kwargs):
  cmd.update(kwargs)
 
  with self._socket_for_reads(session) as (sock_info, slave_ok):
- result = self._command(sock_info, cmd, slave_ok,
- read_concern=self.read_concern,
- session=session)
+ # We call sock_info.command here directly, instead of
+ # calling self._command to avoid using an implicit session.
+ result = sock_info.command(
+ self.__database.name,
+ cmd,
+ slave_ok,
+ self._read_preference_for(session),
+ self.codec_options,
+ read_concern=self.read_concern,
+ parse_write_concern_error=True,
+ session=session,
+ client=self.__database.client)
 
  cursors = []
  for cursor in result['cursors']:
- s = self.__database.client._ensure_session(session)
  cursors.append(CommandCursor(
  self, cursor['cursor'], sock_info.address,
- session=s, explicit_session=session is not None))
+ session=session, explicit_session=session is not None))
 
  return cursors
 

test/test_session.py

@@ -332,12 +332,9 @@ def scan(session=None):
  c.batch_size(2)
  list(c)
 
- self._test_ops(client, (scan, [], {}))
-
- # Implicit session with parallel_scan is uncorrelated with cursors',
- # but each cursor's getMores all use the same lsid.
  listener.results.clear()
- scan()
+ with client.start_session() as session:
+ scan(session)
  cursor_lsids = {}
  for event in listener.results['started']:
  self.assertIn(