From 14c24c9037a7be46f9f79e85d2ce303ada4085e9 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 26 Jul 2019 10:07:21 +0100
Subject: [PATCH 1/2] Fix room summary when rejected events are in state

Annoyingly, `current_state_events` table can include rejected events,
in which case the membership column will be null. To work around this
lets just always filter out null membership for now.
---
 synapse/storage/roommember.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index bfb834ccca..d0fe3a7f78 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -156,9 +156,12 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # then we can avoid a join, which is a Very Good Thing given how
             # frequently this function gets called.
             if self._current_state_events_membership_up_to_date:
+                # Note, rejected events will have a null membership field, so
+                # we we manually filter them out.
                 sql = """
                     SELECT count(*), membership FROM current_state_events
                     WHERE type = 'm.room.member' AND room_id = ?
+                        AND membership IS NOT NULL
                     GROUP BY membership
                 """
             else:
@@ -180,10 +183,13 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # we order by membership and then fairly arbitrarily by event_id so
             # heroes are consistent
             if self._current_state_events_membership_up_to_date:
+                # Note, rejected events will have a null membership field, so
+                # we we manually filter them out.
                 sql = """
                     SELECT state_key, membership, event_id
                     FROM current_state_events
                     WHERE type = 'm.room.member' AND room_id = ?
+                        AND membership IS NOT NULL
                     ORDER BY
                         CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
                         event_id ASC

From 2e9cf7dda5aa5a13e434bf85733747d3d9c2d8e5 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Fri, 26 Jul 2019 10:14:31 +0100
Subject: [PATCH 2/2] Newsfile

---
 changelog.d/5774.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/5774.misc

diff --git a/changelog.d/5774.misc b/changelog.d/5774.misc
new file mode 100644
index 0000000000..5e15dfd5fa
--- /dev/null
+++ b/changelog.d/5774.misc
@@ -0,0 +1 @@
+Reduce database IO usage by optimising queries for current membership.