From 646b4c1bf559df6f17a4f9ea55be0179ee86135e Mon Sep 17 00:00:00 2001
From: Joakim Recht <joakim@beyondwork.ai>
Date: Mon, 22 Jan 2024 13:19:32 +0100
Subject: [PATCH] Only fetch events once for all rooms

---
 syncapi/streams/stream_pdu.go | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/syncapi/streams/stream_pdu.go b/syncapi/streams/stream_pdu.go
index 3abb0b3c6..303148ba2 100644
--- a/syncapi/streams/stream_pdu.go
+++ b/syncapi/streams/stream_pdu.go
@@ -203,6 +203,21 @@ func (p *PDUStreamProvider) IncrementalSync(
 		req.Log.WithError(err).Error("unable to update event filter with ignored users")
 	}
 
+	roomIDs := make([]string, len(stateDeltas))
+	for i := range stateDeltas {
+		roomIDs[i] = stateDeltas[i].RoomID
+	}
+	dbEvents, err := snapshot.RecentEvents(
+		ctx, roomIDs, r,
+		&eventFilter, true, true,
+	)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return r.To
+		}
+		return r.From
+	}
+
 	newPos = from
 	for _, delta := range stateDeltas {
 		newRange := r
@@ -218,7 +233,7 @@ func (p *PDUStreamProvider) IncrementalSync(
 			}
 		}
 		var pos types.StreamPosition
-		if pos, err = p.addRoomDeltaToResponse(ctx, snapshot, req.Device, newRange, delta, &eventFilter, &stateFilter, req); err != nil {
+		if pos, err = p.addRoomDeltaToResponse(ctx, snapshot, req.Device, newRange, delta, &eventFilter, &stateFilter, req, dbEvents); err != nil {
 			req.Log.WithError(err).Error("d.addRoomDeltaToResponse failed")
 			if err == context.DeadlineExceeded || err == context.Canceled || err == sql.ErrTxDone {
 				return newPos
@@ -253,6 +268,7 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 	eventFilter *synctypes.RoomEventFilter,
 	stateFilter *synctypes.StateFilter,
 	req *types.SyncRequest,
+	dbEvents map[string]types.RecentEvents,
 ) (types.StreamPosition, error) {
 	var err error
 	originalLimit := eventFilter.Limit
@@ -265,17 +281,6 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 		}
 	}
 
-	dbEvents, err := snapshot.RecentEvents(
-		ctx, []string{delta.RoomID}, r,
-		eventFilter, true, true,
-	)
-	if err != nil {
-		if err == sql.ErrNoRows {
-			return r.To, nil
-		}
-		return r.From, fmt.Errorf("p.DB.RecentEvents: %w", err)
-	}
-
 	recentStreamEvents := dbEvents[delta.RoomID].Events
 	limited := dbEvents[delta.RoomID].Limited