Try to optimize init syncs by using lateral joins, not getting the

complete state for the current room if we discard it anyway

syncapi/routing/context.go

@@ -159,6 +159,7 @@ func Context(
 	}).Debug("applied history visibility (context eventsBefore/eventsAfter)")
 
 	// TODO: Get the actual state at the last event returned by SelectContextAfterEvent
+	stateFilter.LazyLoadMembers = false
 	state, err := snapshot.CurrentState(ctx, roomID, &stateFilter, nil)
 	if err != nil {
 		logrus.WithError(err).Error("unable to fetch current room state")

syncapi/storage/interface.go

@@ -46,7 +46,7 @@ type DatabaseTransaction interface {
 	RoomIDsWithMembership(ctx context.Context, userID string, membership string) ([]string, error)
 	MembershipCount(ctx context.Context, roomID, membership string, pos types.StreamPosition) (int, error)
 	GetRoomSummary(ctx context.Context, roomID, userID string) (summary *types.Summary, err error)
-	RecentEvents(ctx context.Context, roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) ([]types.StreamEvent, bool, error)
+	RecentEvents(ctx context.Context, roomIDs []string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) (map[string]types.RecentEvents, error)
 	GetBackwardTopologyPos(ctx context.Context, events []*gomatrixserverlib.HeaderedEvent) (types.TopologyToken, error)
 	PositionInTopology(ctx context.Context, eventID string) (pos types.StreamPosition, spos types.StreamPosition, err error)
 	InviteEventsInRange(ctx context.Context, targetUserID string, r types.Range) (map[string]*gomatrixserverlib.HeaderedEvent, map[string]*gomatrixserverlib.HeaderedEvent, types.StreamPosition, error)

syncapi/storage/postgres/current_room_state_table.go

@@ -275,6 +275,15 @@ func (s *currentRoomStateStatements) SelectCurrentState(
 ) ([]*gomatrixserverlib.HeaderedEvent, error) {
 	stmt := sqlutil.TxStmt(txn, s.selectCurrentStateStmt)
 	senders, notSenders := getSendersStateFilterFilter(stateFilter)
+	// We're going to query members later, so remove them from this request
+	if stateFilter.LazyLoadMembers && !stateFilter.IncludeRedundantMembers {
+		notTypes := &[]string{gomatrixserverlib.MRoomMember}
+		if stateFilter.NotTypes != nil {
+			*stateFilter.NotTypes = append(*stateFilter.NotTypes, gomatrixserverlib.MRoomMember)
+		} else {
+			stateFilter.NotTypes = notTypes
+		}
+	}
 	rows, err := stmt.QueryContext(ctx, roomID,
 		pq.StringArray(senders),
 		pq.StringArray(notSenders),

syncapi/storage/postgres/output_room_events_table.go

@@ -21,16 +21,14 @@ import (
 	"encoding/json"
 	"sort"
 
+	"github.com/lib/pq"
 	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/syncapi/storage/postgres/deltas"
 	"github.com/matrix-org/dendrite/syncapi/storage/tables"
 	"github.com/matrix-org/dendrite/syncapi/types"
-
-	"github.com/lib/pq"
 	"github.com/matrix-org/gomatrixserverlib"
-
-	"github.com/matrix-org/dendrite/internal/sqlutil"
 )
 
 const outputRoomEventsSchema = `
@@ -109,14 +107,27 @@ const selectRecentEventsSQL = "" +
 	" AND ( $7::text[] IS NULL OR NOT(type LIKE ANY($7)) )" +
 	" ORDER BY id DESC LIMIT $8"
 
-const selectRecentEventsForSyncSQL = "" +
+const selectRecentEventsForSyncSQL = `
-	"SELECT event_id, id, headered_event_json, session_id, exclude_from_sync, transaction_id, history_visibility FROM syncapi_output_room_events" +
+WITH room_ids AS (
-	" WHERE room_id = $1 AND id > $2 AND id <= $3 AND exclude_from_sync = FALSE" +
+     SELECT unnest($1::text[]) AS room_id
-	" AND ( $4::text[] IS NULL OR     sender  = ANY($4)  )" +
+)
-	" AND ( $5::text[] IS NULL OR NOT(sender  = ANY($5)) )" +
+SELECT    x.*
-	" AND ( $6::text[] IS NULL OR     type LIKE ANY($6)  )" +
+FROM room_ids,
-	" AND ( $7::text[] IS NULL OR NOT(type LIKE ANY($7)) )" +
+          LATERAL  (
-	" ORDER BY id DESC LIMIT $8"
+              SELECT room_id, event_id, id, headered_event_json, session_id, exclude_from_sync, transaction_id, history_visibility
+                    FROM syncapi_output_room_events recent_events
+                    WHERE
+                      recent_events.room_id = room_ids.room_id
+                      AND recent_events.exclude_from_sync = FALSE
+                      AND id > $2 AND id <= $3
+                      AND ( $4::text[] IS NULL OR     sender  = ANY($4)  )
+                      AND ( $5::text[] IS NULL OR NOT(sender  = ANY($5)) )
+                      AND ( $6::text[] IS NULL OR     type LIKE ANY($6)  )
+                      AND ( $7::text[] IS NULL OR NOT(type LIKE ANY($7)) )
+                    ORDER BY recent_events.id DESC
+                    LIMIT $8
+              ) AS x
+`
 
 const selectEarlyEventsSQL = "" +
 	"SELECT event_id, id, headered_event_json, session_id, exclude_from_sync, transaction_id, history_visibility FROM syncapi_output_room_events" +
@@ -396,11 +407,7 @@ func (s *outputRoomEventsStatements) InsertEvent(
 // selectRecentEvents returns the most recent events in the given room, up to a maximum of 'limit'.
 // If onlySyncEvents has a value of true, only returns the events that aren't marked as to exclude
 // from sync.
-func (s *outputRoomEventsStatements) SelectRecentEvents(
+func (s *outputRoomEventsStatements) SelectRecentEvents(ctx context.Context, txn *sql.Tx, roomIDs []string, ra types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) (map[string]types.RecentEvents, error) {
-	ctx context.Context, txn *sql.Tx,
-	roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter,
-	chronologicalOrder bool, onlySyncEvents bool,
-) ([]types.StreamEvent, bool, error) {
 	var stmt *sql.Stmt
 	if onlySyncEvents {
 		stmt = sqlutil.TxStmt(txn, s.selectRecentEventsForSyncStmt)
@@ -408,8 +415,9 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 		stmt = sqlutil.TxStmt(txn, s.selectRecentEventsStmt)
 	}
 	senders, notSenders := getSendersRoomEventFilter(eventFilter)
+
 	rows, err := stmt.QueryContext(
-		ctx, roomID, r.Low(), r.High(),
+		ctx, pq.StringArray(roomIDs), ra.Low(), ra.High(),
 		pq.StringArray(senders),
 		pq.StringArray(notSenders),
 		pq.StringArray(filterConvertTypeWildcardToSQL(eventFilter.Types)),
@@ -417,34 +425,80 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 		eventFilter.Limit+1,
 	)
 	if err != nil {
-		return nil, false, err
+		return nil, err
 	}
 	defer internal.CloseAndLogIfError(ctx, rows, "selectRecentEvents: rows.close() failed")
-	events, err := rowsToStreamEvents(rows)
+
-	if err != nil {
+	result := make(map[string]types.RecentEvents)
-		return nil, false, err
+
+	for rows.Next() {
+		var (
+			roomID            string
+			eventID           string
+			streamPos         types.StreamPosition
+			eventBytes        []byte
+			excludeFromSync   bool
+			sessionID         *int64
+			txnID             *string
+			transactionID     *api.TransactionID
+			historyVisibility gomatrixserverlib.HistoryVisibility
+		)
+		if err := rows.Scan(&roomID, &eventID, &streamPos, &eventBytes, &sessionID, &excludeFromSync, &txnID, &historyVisibility); err != nil {
+			return nil, err
 		}
-	if chronologicalOrder {
+		// TODO: Handle redacted events
-		// The events need to be returned from oldest to latest, which isn't
+		var ev gomatrixserverlib.HeaderedEvent
-		// necessary the way the SQL query returns them, so a sort is necessary to
+		if err := ev.UnmarshalJSONWithEventID(eventBytes, eventID); err != nil {
-		// ensure the events are in the right order in the slice.
+			return nil, err
-		sort.SliceStable(events, func(i int, j int) bool {
-			return events[i].StreamPosition < events[j].StreamPosition
-		})
 		}
-	// we queried for 1 more than the limit, so if we returned one more mark limited=true
+
-	limited := false
+		if sessionID != nil && txnID != nil {
-	if len(events) > eventFilter.Limit {
+			transactionID = &api.TransactionID{
-		limited = true
+				SessionID:     *sessionID,
-		// re-slice the extra (oldest) event out: in chronological order this is the first entry, else the last.
+				TransactionID: *txnID,
-		if chronologicalOrder {
-			events = events[1:]
-		} else {
-			events = events[:len(events)-1]
 			}
 		}
 
-	return events, limited, nil
+		r := result[roomID]
+
+		ev.Visibility = historyVisibility
+		r.Events = append(r.Events, types.StreamEvent{
+			HeaderedEvent:   &ev,
+			StreamPosition:  streamPos,
+			TransactionID:   transactionID,
+			ExcludeFromSync: excludeFromSync,
+		})
+
+		result[roomID] = r
+	}
+
+	if chronologicalOrder {
+		for roomID, evs := range result {
+			// The events need to be returned from oldest to latest, which isn't
+			// necessary the way the SQL query returns them, so a sort is necessary to
+			// ensure the events are in the right order in the slice.
+			sort.SliceStable(evs.Events, func(i int, j int) bool {
+				return evs.Events[i].StreamPosition < evs.Events[j].StreamPosition
+			})
+
+			if len(evs.Events) > eventFilter.Limit {
+				evs.Limited = true
+				evs.Events = evs.Events[1:]
+			}
+
+			result[roomID] = evs
+		}
+	} else {
+		for roomID, evs := range result {
+			if len(evs.Events) > eventFilter.Limit {
+				evs.Limited = true
+				evs.Events = evs.Events[:len(evs.Events)-1]
+			}
+
+			result[roomID] = evs
+		}
+	}
+	return result, rows.Err()
 }
 
 // selectEarlyEvents returns the earliest events in the given room, starting

syncapi/storage/shared/storage_sync.go

@@ -151,8 +151,8 @@ func (d *DatabaseTransaction) GetRoomSummary(ctx context.Context, roomID, userID
 	return summary, nil
 }
 
-func (d *DatabaseTransaction) RecentEvents(ctx context.Context, roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) ([]types.StreamEvent, bool, error) {
+func (d *DatabaseTransaction) RecentEvents(ctx context.Context, roomIDs []string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) (map[string]types.RecentEvents, error) {
-	return d.OutputEvents.SelectRecentEvents(ctx, d.txn, roomID, r, eventFilter, chronologicalOrder, onlySyncEvents)
+	return d.OutputEvents.SelectRecentEvents(ctx, d.txn, roomIDs, r, eventFilter, chronologicalOrder, onlySyncEvents)
 }
 
 func (d *DatabaseTransaction) PositionInTopology(ctx context.Context, eventID string) (pos types.StreamPosition, spos types.StreamPosition, err error) {
@@ -370,20 +370,26 @@ func (d *DatabaseTransaction) GetStateDeltas(
 	}
 
 	// get all the state events ever (i.e. for all available rooms) between these two positions
-	stateNeededFiltered, eventMapFiltered, err := d.OutputEvents.SelectStateInRange(ctx, d.txn, r, stateFilter, allRoomIDs)
+	stateFiltered := state
+	// avoid hitting the database if the result would be the same as above
+	if !isStatefilterEmpty(stateFilter) {
+		var stateNeededFiltered map[string]map[string]bool
+		var eventMapFiltered map[string]types.StreamEvent
+		stateNeededFiltered, eventMapFiltered, err = d.OutputEvents.SelectStateInRange(ctx, d.txn, r, stateFilter, allRoomIDs)
 		if err != nil {
 			if err == sql.ErrNoRows {
 				return nil, nil, nil
 			}
 			return nil, nil, err
 		}
-	stateFiltered, err := d.fetchStateEvents(ctx, d.txn, stateNeededFiltered, eventMapFiltered)
+		stateFiltered, err = d.fetchStateEvents(ctx, d.txn, stateNeededFiltered, eventMapFiltered)
 		if err != nil {
 			if err == sql.ErrNoRows {
 				return nil, nil, nil
 			}
 			return nil, nil, err
 		}
+	}
 
 	// find out which rooms this user is peeking, if any.
 	// We do this before joins so any peeks get overwritten
@@ -701,6 +707,28 @@ func (d *DatabaseTransaction) MaxStreamPositionForRelations(ctx context.Context)
 	return types.StreamPosition(id), err
 }
 
+func isStatefilterEmpty(filter *gomatrixserverlib.StateFilter) bool {
+	if filter == nil {
+		return true
+	}
+	switch {
+	case filter.NotTypes != nil && len(*filter.NotTypes) > 0:
+		return false
+	case filter.Types != nil && len(*filter.Types) > 0:
+		return false
+	case filter.Senders != nil && len(*filter.Senders) > 0:
+		return false
+	case filter.NotSenders != nil && len(*filter.NotSenders) > 0:
+		return false
+	case filter.NotRooms != nil && len(*filter.NotRooms) > 0:
+		return false
+	case filter.ContainsURL != nil:
+		return false
+	default:
+		return true
+	}
+}
+
 func (d *DatabaseTransaction) RelationsFor(ctx context.Context, roomID, eventID, relType, eventType string, from, to types.StreamPosition, backwards bool, limit int) (
 	events []types.StreamEvent, prevBatch, nextBatch string, err error,
 ) {

syncapi/storage/sqlite3/output_room_events_table.go

@@ -366,11 +366,7 @@ func (s *outputRoomEventsStatements) InsertEvent(
 	return streamPos, err
 }
 
-func (s *outputRoomEventsStatements) SelectRecentEvents(
+func (s *outputRoomEventsStatements) SelectRecentEvents(ctx context.Context, txn *sql.Tx, roomIDs []string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) (map[string]types.RecentEvents, error) {
-	ctx context.Context, txn *sql.Tx,
-	roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter,
-	chronologicalOrder bool, onlySyncEvents bool,
-) ([]types.StreamEvent, bool, error) {
 	var query string
 	if onlySyncEvents {
 		query = selectRecentEventsForSyncSQL
@@ -381,25 +377,25 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 	stmt, params, err := prepareWithFilters(
 		s.db, txn, query,
 		[]interface{}{
-			roomID, r.Low(), r.High(),
+			roomIDs, r.Low(), r.High(),
 		},
 		eventFilter.Senders, eventFilter.NotSenders,
 		eventFilter.Types, eventFilter.NotTypes,
 		nil, eventFilter.ContainsURL, eventFilter.Limit+1, FilterOrderDesc,
 	)
 	if err != nil {
-		return nil, false, fmt.Errorf("s.prepareWithFilters: %w", err)
+		return nil, fmt.Errorf("s.prepareWithFilters: %w", err)
 	}
 	defer internal.CloseAndLogIfError(ctx, stmt, "selectRecentEvents: stmt.close() failed")
 
 	rows, err := stmt.QueryContext(ctx, params...)
 	if err != nil {
-		return nil, false, err
+		return nil, err
 	}
 	defer internal.CloseAndLogIfError(ctx, rows, "selectRecentEvents: rows.close() failed")
 	events, err := rowsToStreamEvents(rows)
 	if err != nil {
-		return nil, false, err
+		return nil, err
 	}
 	if chronologicalOrder {
 		// The events need to be returned from oldest to latest, which isn't
@@ -410,9 +406,7 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 		})
 	}
 	// we queried for 1 more than the limit, so if we returned one more mark limited=true
-	limited := false
 	if len(events) > eventFilter.Limit {
-		limited = true
 		// re-slice the extra (oldest) event out: in chronological order this is the first entry, else the last.
 		if chronologicalOrder {
 			events = events[1:]
@@ -420,7 +414,7 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 			events = events[:len(events)-1]
 		}
 	}
-	return events, limited, nil
+	return map[string]types.RecentEvents{}, nil
 }
 
 func (s *outputRoomEventsStatements) SelectEarlyEvents(

syncapi/storage/storage_test.go

@@ -156,12 +156,12 @@ func TestRecentEventsPDU(t *testing.T) {
 			tc := testCases[i]
 			t.Run(tc.Name, func(st *testing.T) {
 				var filter gomatrixserverlib.RoomEventFilter
-				var gotEvents []types.StreamEvent
+				var gotEvents map[string]types.RecentEvents
 				var limited bool
 				filter.Limit = tc.Limit
 				WithSnapshot(t, db, func(snapshot storage.DatabaseTransaction) {
 					var err error
-					gotEvents, limited, err = snapshot.RecentEvents(ctx, r.ID, types.Range{
+					gotEvents, err = snapshot.RecentEvents(ctx, []string{r.ID}, types.Range{
 						From: tc.From,
 						To:   tc.To,
 					}, &filter, !tc.ReverseOrder, true)
@@ -169,15 +169,18 @@ func TestRecentEventsPDU(t *testing.T) {
 						st.Fatalf("failed to do sync: %s", err)
 					}
 				})
+				streamEvents := gotEvents[r.ID]
+				limited = streamEvents.Limited
 				if limited != tc.WantLimited {
 					st.Errorf("got limited=%v want %v", limited, tc.WantLimited)
 				}
-				if len(gotEvents) != len(tc.WantEvents) {
+				if len(streamEvents.Events) != len(tc.WantEvents) {
 					st.Errorf("got %d events, want %d", len(gotEvents), len(tc.WantEvents))
 				}
-				for j := range gotEvents {
+
-					if !reflect.DeepEqual(gotEvents[j].JSON(), tc.WantEvents[j].JSON()) {
+				for j := range streamEvents.Events {
-						st.Errorf("event %d got %s want %s", j, string(gotEvents[j].JSON()), string(tc.WantEvents[j].JSON()))
+					if !reflect.DeepEqual(streamEvents.Events[j].JSON(), tc.WantEvents[j].JSON()) {
+						st.Errorf("event %d got %s want %s", j, string(streamEvents.Events[j].JSON()), string(tc.WantEvents[j].JSON()))
 					}
 				}
 			})

syncapi/storage/tables/interface.go

@@ -66,7 +66,7 @@ type Events interface {
 	// SelectRecentEvents returns events between the two stream positions: exclusive of low and inclusive of high.
 	// If onlySyncEvents has a value of true, only returns the events that aren't marked as to exclude from sync.
 	// Returns up to `limit` events. Returns `limited=true` if there are more events in this range but we hit the `limit`.
-	SelectRecentEvents(ctx context.Context, txn *sql.Tx, roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) ([]types.StreamEvent, bool, error)
+	SelectRecentEvents(ctx context.Context, txn *sql.Tx, roomIDs []string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) (map[string]types.RecentEvents, error)
 	// SelectEarlyEvents returns the earliest events in the given room.
 	SelectEarlyEvents(ctx context.Context, txn *sql.Tx, roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter) ([]types.StreamEvent, error)
 	SelectEvents(ctx context.Context, txn *sql.Tx, eventIDs []string, filter *gomatrixserverlib.RoomEventFilter, preserveOrder bool) ([]types.StreamEvent, error)

syncapi/streams/stream_pdu.go

@@ -82,19 +82,30 @@ func (p *PDUStreamProvider) CompleteSync(
 		req.Log.WithError(err).Error("unable to update event filter with ignored users")
 	}
 
+	s := time.Now()
+	recentEvents, err := snapshot.RecentEvents(ctx, joinedRoomIDs, r, &eventFilter, true, true)
+	if err != nil {
+		return from
+	}
+	logrus.WithFields(logrus.Fields{
+		"duration": time.Since(s),
+		"rooms":    len(joinedRoomIDs)}).
+		Debugf("got recent events for all rooms")
+	// Build up a /sync response. Add joined rooms.
+	s = time.Now()
+	for _, roomID := range joinedRoomIDs {
+		events := recentEvents[roomID]
 		// Invalidate the lazyLoadCache, otherwise we end up with missing displaynames/avatars
 		// TODO: This might be inefficient, when joined to many and/or large rooms.
-	for _, roomID := range joinedRoomIDs {
 		joinedUsers := p.notifier.JoinedUsers(roomID)
 		for _, sharedUser := range joinedUsers {
 			p.lazyLoadCache.InvalidateLazyLoadedUser(req.Device, roomID, sharedUser)
 		}
-	}
 
-	// Build up a /sync response. Add joined rooms.
+		// get the join response for each room
-	for _, roomID := range joinedRoomIDs {
 		jr, jerr := p.getJoinResponseForCompleteSync(
-			ctx, snapshot, roomID, r, &stateFilter, &eventFilter, req.WantFullState, req.Device, false,
+			ctx, snapshot, roomID, &stateFilter, req.WantFullState, req.Device, false,
+			events.Events, events.Limited,
 		)
 		if jerr != nil {
 			req.Log.WithError(jerr).Error("p.getJoinResponseForCompleteSync failed")
@@ -106,6 +117,10 @@ func (p *PDUStreamProvider) CompleteSync(
 		req.Response.Rooms.Join[roomID] = jr
 		req.Rooms[roomID] = gomatrixserverlib.Join
 	}
+	logrus.WithFields(logrus.Fields{
+		"duration": time.Since(s),
+		"rooms":    len(joinedRoomIDs)}).
+		Debugf("built join response for all rooms")
 
 	// Add peeked rooms.
 	peeks, err := snapshot.PeeksInRange(ctx, req.Device.UserID, req.Device.ID, r)
@@ -113,11 +128,25 @@ func (p *PDUStreamProvider) CompleteSync(
 		req.Log.WithError(err).Error("p.DB.PeeksInRange failed")
 		return from
 	}
+	if len(peeks) > 0 {
+		peekRooms := make([]string, 0, len(peeks))
 		for _, peek := range peeks {
 			if !peek.Deleted {
+				peekRooms = append(peekRooms, peek.RoomID)
+			}
+		}
+
+		recentEvents, err = snapshot.RecentEvents(ctx, peekRooms, r, &eventFilter, true, true)
+		if err != nil {
+			return from
+		}
+
+		for _, roomID := range peekRooms {
 			var jr *types.JoinResponse
+			events := recentEvents[roomID]
 			jr, err = p.getJoinResponseForCompleteSync(
-				ctx, snapshot, peek.RoomID, r, &stateFilter, &eventFilter, req.WantFullState, req.Device, true,
+				ctx, snapshot, roomID, &stateFilter, req.WantFullState, req.Device, true,
+				events.Events, events.Limited,
 			)
 			if err != nil {
 				req.Log.WithError(err).Error("p.getJoinResponseForCompleteSync failed")
@@ -126,7 +155,7 @@ func (p *PDUStreamProvider) CompleteSync(
 				}
 				continue
 			}
-			req.Response.Rooms.Peek[peek.RoomID] = jr
+			req.Response.Rooms.Peek[roomID] = jr
 		}
 	}
 
@@ -227,7 +256,7 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 	stateFilter *gomatrixserverlib.StateFilter,
 	req *types.SyncRequest,
 ) (types.StreamPosition, error) {
-
+	var err error
 	originalLimit := eventFilter.Limit
 	// If we're going backwards, grep at least X events, this is mostly to satisfy Sytest
 	if r.Backwards && originalLimit < recentEventBackwardsLimit {
@@ -238,8 +267,8 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 		}
 	}
 
-	recentStreamEvents, limited, err := snapshot.RecentEvents(
+	dbEvents, err := snapshot.RecentEvents(
-		ctx, delta.RoomID, r,
+		ctx, []string{delta.RoomID}, r,
 		eventFilter, true, true,
 	)
 	if err != nil {
@@ -248,6 +277,10 @@ func (p *PDUStreamProvider) addRoomDeltaToResponse(
 		}
 		return r.From, fmt.Errorf("p.DB.RecentEvents: %w", err)
 	}
+
+	recentStreamEvents := dbEvents[delta.RoomID].Events
+	limited := dbEvents[delta.RoomID].Limited
+
 	recentEvents := gomatrixserverlib.HeaderedReverseTopologicalOrdering(
 		snapshot.StreamEventsToEvents(device, recentStreamEvents),
 		gomatrixserverlib.TopologicalOrderByPrevEvents,
@@ -428,25 +461,16 @@ func (p *PDUStreamProvider) getJoinResponseForCompleteSync(
 	ctx context.Context,
 	snapshot storage.DatabaseTransaction,
 	roomID string,
-	r types.Range,
 	stateFilter *gomatrixserverlib.StateFilter,
-	eventFilter *gomatrixserverlib.RoomEventFilter,
 	wantFullState bool,
 	device *userapi.Device,
 	isPeek bool,
+	recentStreamEvents []types.StreamEvent,
+	limited bool,
 ) (jr *types.JoinResponse, err error) {
 	jr = types.NewJoinResponse()
 	// TODO: When filters are added, we may need to call this multiple times to get enough events.
 	//       See: https://github.com/matrix-org/synapse/blob/v0.19.3/synapse/handlers/sync.py#L316
-	recentStreamEvents, limited, err := snapshot.RecentEvents(
-		ctx, roomID, r, eventFilter, true, true,
-	)
-	if err != nil {
-		if err == sql.ErrNoRows {
-			return jr, nil
-		}
-		return
-	}
 
 	// Work our way through the timeline events and pick out the event IDs
 	// of any state events that appear in the timeline. We'll specifically

syncapi/types/types.go

@@ -63,6 +63,11 @@ type StreamEvent struct {
 	ExcludeFromSync bool
 }
 
+type RecentEvents struct {
+	Limited bool
+	Events  []StreamEvent
+}
+
 // Range represents a range between two stream positions.
 type Range struct {
 	// From is the position the client has already received.