From 45df38e61bb876208d032cf3480230cecff6cdd8 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Thu, 25 Jul 2019 17:15:54 +0100
Subject: [PATCH 1/3] Fix current_state bg update to work on old SQLite

---
 synapse/storage/roommember.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index cb88e49b51..a1b9fd8199 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -870,10 +870,10 @@ class RoomMemberStore(RoomMemberWorkerStore):
                 next_room, = row
 
                 sql = """
-                    UPDATE current_state_events AS c
+                    UPDATE current_state_events
                     SET membership = (
                         SELECT membership FROM room_memberships
-                        WHERE event_id = c.event_id
+                        WHERE event_id = current_state_events.event_id
                     )
                     WHERE room_id = ?
                 """

From 84c6ea1af8383049333213e108941a7831b2a4fd Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Mon, 29 Jul 2019 13:04:50 +0100
Subject: [PATCH 2/3] Update old deps unit test to use old sqlite3

---
 .buildkite/pipeline.yml | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index c8ae1a44be..b75269a155 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -49,14 +49,15 @@ steps:
 
 
   - command:
-      - "python -m pip install tox"
+      - "apt-get update && apt-get install -y python3.5 python3.5-dev python3-pip libxml2-dev libxslt-dev zlib1g-dev"
+      - "python3.5 -m pip install tox"
       - "tox -e py35-old,codecov"
     label: ":python: 3.5 / SQLite / Old Deps"
     env:
       TRIAL_FLAGS: "-j 2"
     plugins:
       - docker#v3.0.1:
-          image: "python:3.5"
+          image: "ubuntu:xenial"  # We use xenail to get an old sqlite and python
           propagate-environment: true
     retry:
       automatic:

From d94916852fed15806202d58d903a8b43ff7b4367 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Thu, 25 Jul 2019 17:17:20 +0100
Subject: [PATCH 3/3] Newsfile

---
 changelog.d/5770.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/5770.misc

diff --git a/changelog.d/5770.misc b/changelog.d/5770.misc
new file mode 100644
index 0000000000..5e15dfd5fa
--- /dev/null
+++ b/changelog.d/5770.misc
@@ -0,0 +1 @@
+Reduce database IO usage by optimising queries for current membership.