Add membership column to current_state_events table.

It turns out that doing a join is surprisingly expensive for the DB to
do when room_membership table is larger than the disk cache.

1 files changed, 14 insertions, 12 deletions

diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index b486ca50eb..b70457bfc6 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -918,8 +918,6 @@ class EventsStore(
         min_stream_order = events_and_contexts[0][0].internal_metadata.stream_ordering
         max_stream_order = events_and_contexts[-1][0].internal_metadata.stream_ordering
 
-        self._update_current_state_txn(txn, state_delta_for_room, min_stream_order)
-
         self._update_forward_extremities_txn(
             txn,
             new_forward_extremities=new_forward_extremeties,
@@ -993,6 +991,10 @@ class EventsStore(
             backfilled=backfilled,
         )
 
+        # We call this last as it assumes we've inserted the events into
+        # room_memberships, where applicable.
+        self._update_current_state_txn(txn, state_delta_for_room, min_stream_order)
+
     def _update_current_state_txn(self, txn, state_delta_by_room, stream_id):
         for room_id, current_state_tuple in iteritems(state_delta_by_room):
             to_delete, to_insert = current_state_tuple
@@ -1062,16 +1064,16 @@ class EventsStore(
                 ),
             )
 
-            self._simple_insert_many_txn(
-                txn,
-                table="current_state_events",
-                values=[
-                    {
-                        "event_id": ev_id,
-                        "room_id": room_id,
-                        "type": key[0],
-                        "state_key": key[1],
-                    }
+            # We include the membership in the current state table, hence we do
+            # a lookup when we insert. This assumes that all events have already
+            # been inserted into room_memberships.
+            txn.executemany(
+                """INSERT INTO current_state_events
+                    (room_id, type, state_key, event_id, membership)
+                VALUES (?, ?, ?, ?, (SELECT membership FROM room_memberships WHERE event_id = ?))
+                """,
+                [
+                    (room_id, key[0], key[1], ev_id, ev_id)
                     for key, ev_id in iteritems(to_insert)
                 ],
             )