From 5ac75fc9a2d80ddf2974d281c381f82515606403 Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Thu, 30 May 2019 15:26:55 +0100
Subject: [PATCH] Join against events to use its room_id index

---
 synapse/storage/events_worker.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index b56c83e460..1782428048 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -618,7 +618,12 @@ class EventsWorkerStore(SQLBaseStore):
         """
         See get_total_state_event_counts.
         """
-        sql = "SELECT COUNT(*) FROM state_events WHERE room_id=?"
+        # We join against the events table as that has an index on room_id
+        sql = """
+            SELECT COUNT(*) FROM state_events
+            INNER JOIN events USING (room_id, event_id)
+            WHERE room_id=?
+        """
         txn.execute(sql, (room_id,))
         row = txn.fetchone()
         return row[0] if row else 0