From a23749efbacdf37251faa6662eec08f5287b024a Mon Sep 17 00:00:00 2001
From: Eric Eastwood <contact@ericeastwood.com>
Date: Tue, 6 Jun 2023 15:12:13 -0500
Subject: [PATCH 1/2] No need for the extra join since membership is built-in
 to `current_state_events`

`current_state_events` was added in https://github.com/matrix-org/synapse/pull/5706
and https://github.com/matrix-org/synapse/pull/13745
---
 synapse/storage/databases/main/roommember.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index ae9c201b87e8..1b8ec67f5487 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -927,11 +927,10 @@ async def _check_host_room_membership(
             raise Exception("Invalid host name")
 
         sql = """
-            SELECT state_key FROM current_state_events AS c
-            INNER JOIN room_memberships AS m USING (event_id)
-            WHERE m.membership = ?
+            SELECT state_key FROM current_state_events
+            WHERE membership = ?
                 AND type = 'm.room.member'
-                AND c.room_id = ?
+                AND room_id = ?
                 AND state_key LIKE ?
             LIMIT 1
         """

From 81027ea60ca7f6e64395ea3b0bae995b761e554c Mon Sep 17 00:00:00 2001
From: Eric Eastwood <contact@ericeastwood.com>
Date: Tue, 6 Jun 2023 15:28:55 -0500
Subject: [PATCH 2/2] Add changelog

---
 changelog.d/15731.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/15731.misc

diff --git a/changelog.d/15731.misc b/changelog.d/15731.misc
new file mode 100644
index 000000000000..906bc2696254
--- /dev/null
+++ b/changelog.d/15731.misc
@@ -0,0 +1 @@
+Remove redundant table join with `room_memberships` when doing a `is_host_joined()`/`is_host_invited()` call (`membership` is already part of the `current_state_events`).