From 72626b78ef4aa9ab0bd11e332495f34bd43bbc26 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 27 Oct 2021 12:33:21 +0100
Subject: [PATCH] Fix thread BG update to not seq scan event_json (#11192)
For some reason the query optimiser decided to seq scan both tables,
rather than index scanning `event_json`.
---
changelog.d/11192.feature | 1 +
synapse/storage/databases/main/events_bg_updates.py | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
create mode 100644 changelog.d/11192.feature
diff --git a/changelog.d/11192.feature b/changelog.d/11192.feature
new file mode 100644
index 0000000000..76b0d28084
--- /dev/null
+++ b/changelog.d/11192.feature
@@ -0,0 +1 @@
+Experimental support for the thread relation defined in [MSC3440](https://github.com/matrix-org/matrix-doc/pull/3440).
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
index f92d824876..ae3a8a63e4 100644
--- a/synapse/storage/databases/main/events_bg_updates.py
+++ b/synapse/storage/databases/main/events_bg_updates.py
@@ -1108,7 +1108,7 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
"""
SELECT event_id, json FROM event_json
LEFT JOIN event_relations USING (event_id)
- WHERE event_id > ? AND relates_to_id IS NULL
+ WHERE event_id > ? AND event_relations.event_id IS NULL
ORDER BY event_id LIMIT ?
""",
(last_event_id, batch_size),
--
GitLab