messages: Save a database query in check_message code path.

The flow in recipient_for_user_profiles previously worked by doing
validation on UserProfile objects (returning a list of IDs), and then
using that data to look up the appropriate Recipient objects.

For the case of sending a private message to another user, the new
UserProfile.recipient column lets us avoid the query to the Recipient
table if we move the step of reducing down to user IDs to only occur
in the Huddle code path.

zerver/lib/actions.py

@@ -1904,13 +1904,15 @@ def create_streams_if_needed(realm: Realm,
     return added_streams, existing_streams
 
 
-def get_recipient_from_user_ids(recipient_profile_ids: Set[int],
-                                forwarded_mirror_message: bool,
-                                forwarder_user_profile: Optional[UserProfile],
-                                sender: UserProfile) -> Recipient:
+def get_recipient_from_user_profiles(recipient_profiles: Sequence[UserProfile],
+                                     forwarded_mirror_message: bool,
+                                     forwarder_user_profile: Optional[UserProfile],
+                                     sender: UserProfile) -> Recipient:
 
-    # Avoid mutating the passed in set of recipient_profile_ids.
-    recipient_profile_ids = set(recipient_profile_ids)
+    # Avoid mutating the passed in list of recipient_profiles.
+    recipient_profiles_map = {}
+    for user_profile in recipient_profiles:
+        recipient_profiles_map[user_profile.id] = user_profile
 
     if forwarded_mirror_message:
         # In our mirroring integrations with some third-party
@@ -1922,25 +1924,26 @@ def get_recipient_from_user_ids(recipient_profile_ids: Set[int],
         # for whether forwarder_user_profile is among the private
         # message recipients of the message.
         assert forwarder_user_profile is not None
-        if forwarder_user_profile.id not in recipient_profile_ids:
+        if forwarder_user_profile.id not in recipient_profiles_map:
             raise ValidationError(_("User not authorized for this query"))
 
     # If the private message is just between the sender and
     # another person, force it to be a personal internally
-    if (len(recipient_profile_ids) == 2 and sender.id in recipient_profile_ids):
-        recipient_profile_ids.remove(sender.id)
+    if (len(recipient_profiles_map) == 2 and sender.id in recipient_profiles_map):
+        del recipient_profiles_map[sender.id]
 
-    if len(recipient_profile_ids) > 1:
+    if len(recipient_profiles_map) > 1:
         # Make sure the sender is included in huddle messages
-        recipient_profile_ids.add(sender.id)
-        return get_huddle_recipient(recipient_profile_ids)
+        recipient_profiles_map[sender.id] = sender
+        user_ids = set([user_id for user_id in recipient_profiles_map])  # type: Set[int]
+        return get_huddle_recipient(user_ids)
     else:
-        return get_personal_recipient(list(recipient_profile_ids)[0])
+        return list(recipient_profiles_map.values())[0].recipient
 
 def validate_recipient_user_profiles(user_profiles: Sequence[UserProfile],
                                      sender: UserProfile,
-                                     allow_deactivated: bool=False) -> Set[int]:
-    recipient_profile_ids = set()
+                                     allow_deactivated: bool=False) -> Sequence[UserProfile]:
+    recipient_profiles_map = {}  # type: Dict[int, UserProfile]
 
     # We exempt cross-realm bots from the check that all the recipients
     # are in the same realm.
@@ -1952,14 +1955,14 @@ def validate_recipient_user_profiles(user_profiles: Sequence[UserProfile],
         if (not user_profile.is_active and not user_profile.is_mirror_dummy and
                 not allow_deactivated) or user_profile.realm.deactivated:
             raise ValidationError(_("'%s' is no longer using Zulip.") % (user_profile.email,))
-        recipient_profile_ids.add(user_profile.id)
+        recipient_profiles_map[user_profile.id] = user_profile
         if not is_cross_realm_bot_email(user_profile.email):
             realms.add(user_profile.realm_id)
 
     if len(realms) > 1:
         raise ValidationError(_("You can't send private messages outside of your organization."))
 
-    return recipient_profile_ids
+    return list(recipient_profiles_map.values())
 
 def recipient_for_emails(emails: Iterable[str], forwarded_mirror_message: bool,
                          forwarder_user_profile: Optional[UserProfile],
@@ -2003,11 +2006,11 @@ def recipient_for_user_profiles(user_profiles: Sequence[UserProfile], forwarded_
                                 forwarder_user_profile: Optional[UserProfile],
                                 sender: UserProfile, allow_deactivated: bool=False) -> Recipient:
 
-    recipient_profile_ids = validate_recipient_user_profiles(user_profiles, sender,
-                                                             allow_deactivated=allow_deactivated)
+    recipient_profiles = validate_recipient_user_profiles(user_profiles, sender,
+                                                          allow_deactivated=allow_deactivated)
 
-    return get_recipient_from_user_ids(recipient_profile_ids, forwarded_mirror_message,
-                                       forwarder_user_profile, sender)
+    return get_recipient_from_user_profiles(recipient_profiles, forwarded_mirror_message,
+                                            forwarder_user_profile, sender)
 
 def already_sent_mirrored_message_id(message: Message) -> Optional[int]:
     if message.recipient.type == Recipient.HUDDLE:

zerver/tests/test_signup.py

@@ -517,7 +517,7 @@ class LoginTest(ZulipTestCase):
         with queries_captured() as queries:
             self.register(self.nonreg_email('test'), "test")
         # Ensure the number of queries we make is not O(streams)
-        self.assertEqual(len(queries), 81)
+        self.assertEqual(len(queries), 80)
         user_profile = self.nonreg_user('test')
         self.assert_logged_in_user_id(user_profile.id)
         self.assertFalse(user_profile.enable_stream_desktop_notifications)