4 files changed, 8 insertions, 1 deletions
diff --git a/changelog.d/6148.misc b/changelog.d/6148.misc
new file mode 100644
index 0000000000..1d5213345c
--- /dev/null
+++ b/changelog.d/6148.misc
@@ -0,0 +1 @@
+Improve performance of `find_next_generated_user_id` DB query.
diff --git a/changelog.d/6153.misc b/changelog.d/6153.misc
new file mode 100644
index 0000000000..dfee73c28f
--- /dev/null
+++ b/changelog.d/6153.misc
@@ -0,0 +1 @@
+Improve performance of the public room list directory.
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 241a7be51e..1a859352b6 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -493,7 +493,9 @@ class RegistrationWorkerStore(SQLBaseStore):
         """
 
         def _find_next_generated_user_id(txn):
-            txn.execute("SELECT name FROM users")
+            # We bound between '@1' and '@a' to avoid pulling the entire table
+            # out.
+            txn.execute("SELECT name FROM users WHERE '@1' <= name AND name < '@a'")
 
             regex = re.compile(r"^@(\d+):")
 
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index 70bd719521..43cc56fa6f 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -192,6 +192,9 @@ class RoomWorkerStore(SQLBaseStore):
 
             query_args += [last_joined_members, last_joined_members, last_room_id]
 
+        if ignore_non_federatable:
+            where_clauses.append("is_federatable")
+
         if search_filter and search_filter.get("generic_search_term", None):
             search_term = "%" + search_filter["generic_search_term"] + "%"