address review

Author: blink1073

doc/changelog.rst

@@ -10,6 +10,7 @@ PyMongo 4.14 brings a number of changes including:
 - Added :meth:`pymongo.asynchronous.mongo_client.AsyncMongoClient.append_metadata` and
   :meth:`pymongo.mongo_client.MongoClient.append_metadata` to allow instantiated MongoClients to send client metadata
   on-demand
+- Improved performance of selecting a server with the Primary selector.
 
 - Introduces a minor breaking change. When encoding :class:`bson.binary.BinaryVector`, a ``ValueError`` will be raised
   if the 'padding' metadata field is < 0 or > 7, or non-zero for any type other than PACKED_BIT.

pymongo/topology_description.py

@@ -325,9 +325,7 @@ def apply_selector(
             return [description] if description else []
 
         # Primary selection fast path.
-        if self.topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary and isinstance(
-            selector, Primary
-        ):
+        if self.topology_type == TOPOLOGY_TYPE.ReplicaSetWithPrimary and type(selector) is Primary:
             for sd in self._server_descriptions.values():
                 if sd.server_type == SERVER_TYPE.RSPrimary:
                     return [sd]