fix: filter learner search by requested usernames instead of scanning…

forum/api/users.py

@@ -293,11 +293,10 @@ def _get_stats_for_usernames(
     course_id: str, usernames: list[str], backend: Any
 ) -> list[dict[str, Any]]:
     """Get stats for specific usernames."""
-    users = backend.get_users()
+    users = backend.get_users(username__in=usernames)
+
     stats_query = []
     for user in users:
-        if user["username"] not in usernames:
-            continue
         course_stats = user.get("course_stats")
         if course_stats:
             for course_stat in course_stats:

forum/backends/mysql/api.py

@@ -2157,8 +2157,13 @@ def get_users(**kwargs: Any) -> list[dict[str, Any]]:
         Returns:
             A list of users.
         """
+        kwargs = kwargs.copy()
+        sort_key = kwargs.pop("sort_key", None)
+        username_in = kwargs.pop("username__in", None)
+        if username_in is not None:
+            kwargs["user__username__in"] = username_in
+
         forum_users = ForumUser.objects.filter(**kwargs)
-        sort_key = kwargs.get("sort_key")
         if sort_key:
             forum_users = forum_users.order_by(sort_key)