message: Merge unnecessary cache_transformer step.

Having a non-identity `cache_transformer` is no different from running
it on every row of the query_function.  Simplify understanding of the
codepath used in caching by merging the pieces of code.

zerver/lib/message.py

@@ -218,15 +218,14 @@ def messages_for_ids(
     user_profile: Optional[UserProfile],
     realm: Realm,
 ) -> List[Dict[str, Any]]:
-    cache_transformer = MessageDict.build_dict_from_raw_db_row
     id_fetcher = lambda row: row["id"]
 
     message_dicts = generic_bulk_cached_fetch(
         to_dict_cache_key_id,
-        MessageDict.get_raw_db_rows,
+        MessageDict.ids_to_dict,
         message_ids,
         id_fetcher=id_fetcher,
-        cache_transformer=cache_transformer,
+        cache_transformer=lambda obj: obj,
         extractor=extract_message_dict,
         setter=stringify_message_dict,
     )

zerver/lib/message_cache.py

@@ -321,7 +321,7 @@ class MessageDict:
         return [MessageDict.build_dict_from_raw_db_row(row) for row in message_rows]
 
     @staticmethod
-    def get_raw_db_rows(needed_ids: List[int]) -> List[Dict[str, Any]]:
+    def ids_to_dict(needed_ids: List[int]) -> List[Dict[str, Any]]:
         # This is a special purpose function optimized for
         # callers like get_messages_backend().
         fields = [
@@ -342,7 +342,8 @@ class MessageDict:
         ]
         # Uses index: zerver_message_pkey
         messages = Message.objects.filter(id__in=needed_ids).values(*fields)
-        return MessageDict.sew_submessages_and_reactions_to_msgs(messages)
+        MessageDict.sew_submessages_and_reactions_to_msgs(messages)
+        return [MessageDict.build_dict_from_raw_db_row(row) for row in messages]
 
     @staticmethod
     def build_dict_from_raw_db_row(row: Dict[str, Any]) -> Dict[str, Any]:

zerver/tests/test_message_dict.py

@@ -171,14 +171,12 @@ class MessageDictTest(ZulipTestCase):
         self.assertTrue(num_ids >= 600)
 
         with self.assert_database_query_count(7):
-            rows = list(MessageDict.get_raw_db_rows(ids))
-
-            objs = [MessageDict.build_dict_from_raw_db_row(row) for row in rows]
+            objs = MessageDict.ids_to_dict(ids)
             MessageDict.post_process_dicts(
                 objs, apply_markdown=False, client_gravatar=False, realm=realm
             )
 
-        self.assert_length(rows, num_ids)
+        self.assert_length(objs, num_ids)
 
     def test_applying_markdown(self) -> None:
         sender = self.example_user("othello")
@@ -200,8 +198,7 @@ class MessageDictTest(ZulipTestCase):
 
         # An important part of this test is to get the message through this exact code path,
         # because there is an ugly hack we need to cover.  So don't just say "row = message".
-        row = MessageDict.get_raw_db_rows([message.id])[0]
-        dct = MessageDict.build_dict_from_raw_db_row(row)
+        dct = MessageDict.ids_to_dict([message.id])[0]
         expected_content = "<p>hello <strong>world</strong></p>"
         self.assertEqual(dct["rendered_content"], expected_content)
         message = Message.objects.get(id=message.id)
@@ -231,8 +228,7 @@ class MessageDictTest(ZulipTestCase):
 
         # An important part of this test is to get the message through this exact code path,
         # because there is an ugly hack we need to cover.  So don't just say "row = message".
-        row = MessageDict.get_raw_db_rows([message.id])[0]
-        dct = MessageDict.build_dict_from_raw_db_row(row)
+        dct = MessageDict.ids_to_dict([message.id])[0]
         error_content = (
             "<p>[Zulip note: Sorry, we could not understand the formatting of your message]</p>"
         )
@@ -298,8 +294,7 @@ class MessageDictTest(ZulipTestCase):
         reaction = Reaction.objects.create(
             message=message, user_profile=sender, emoji_name="simple_smile"
         )
-        row = MessageDict.get_raw_db_rows([message.id])[0]
-        msg_dict = MessageDict.build_dict_from_raw_db_row(row)
+        msg_dict = MessageDict.ids_to_dict([message.id])[0]
         self.assertEqual(msg_dict["reactions"][0]["emoji_name"], reaction.emoji_name)
         self.assertEqual(msg_dict["reactions"][0]["user_id"], sender.id)
         self.assertEqual(msg_dict["reactions"][0]["user"]["id"], sender.id)

zerver/tests/test_message_send.py

@@ -1699,8 +1699,7 @@ class StreamMessagesTest(ZulipTestCase):
             self.example_user("hamlet"), "Denmark", content="whatever", topic_name="my topic"
         )
         message = most_recent_message(user_profile)
-        row = MessageDict.get_raw_db_rows([message.id])[0]
-        dct = MessageDict.build_dict_from_raw_db_row(row)
+        dct = MessageDict.ids_to_dict([message.id])[0]
         MessageDict.post_process_dicts(
             [dct],
             apply_markdown=True,

zerver/tests/test_submessage.py

@@ -65,7 +65,7 @@ class TestBasics(ZulipTestCase):
         rows.sort(key=lambda r: r["id"])
         self.assertEqual(rows, expected_data)
 
-        msg_rows = MessageDict.get_raw_db_rows([message_id])
+        msg_rows = MessageDict.ids_to_dict([message_id])
         rows = msg_rows[0]["submessages"]
         rows.sort(key=lambda r: r["id"])
         self.assertEqual(rows, expected_data)