Optimize /sync and history visibility (#2961)

Should fix the following issues or make a lot less worse when using
Postgres:

The main issue behind #2911: The client gives up after a certain time,
causing a cascade of context errors, because the response couldn't be
built up fast enough. This mostly happens on accounts with many rooms,
due to the inefficient way we're getting recent events and current state

For #2777: The queries for getting the membership events for history
visibility were being executed for each room (I think 185?), resulting
in a whooping 2k queries for membership events. (Getting the
statesnapshot -> block nids -> actual wanted membership event)

Both should now be better by:
- Using a LATERAL join to get all recent events for all joined rooms in
one go (TODO: maybe do the same for room summary and current state etc)
- If we're lazy loading on initial syncs, we're now not getting the
whole current state, just to drop the majority of it because we're lazy
loading members - we add a filter to exclude membership events on the
first call to `CurrentState`.
- Using an optimized query to get the membership events needed to
calculate history visibility

---------

Co-authored-by: kegsay <kegan@matrix.org>

syncapi/storage/sqlite3/account_data_table.go

@@ -105,7 +105,9 @@ func (s *accountDataStatements) SelectAccountDataInRange(
 		filter.Senders, filter.NotSenders,
 		filter.Types, filter.NotTypes,
 		[]string{}, nil, filter.Limit, FilterOrderAsc)
-
+	if err != nil {
+		return
+	}
 	rows, err := stmt.QueryContext(ctx, params...)
 	if err != nil {
 		return

syncapi/storage/sqlite3/current_room_state_table.go

@@ -267,6 +267,15 @@ func (s *currentRoomStateStatements) SelectCurrentState(
 	stateFilter *gomatrixserverlib.StateFilter,
 	excludeEventIDs []string,
 ) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	// 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
+		}
+	}
 	stmt, params, err := prepareWithFilters(
 		s.db, txn, selectCurrentStateSQL,
 		[]interface{}{

syncapi/storage/sqlite3/output_room_events_table.go

@@ -368,9 +368,9 @@ func (s *outputRoomEventsStatements) InsertEvent(
 
 func (s *outputRoomEventsStatements) SelectRecentEvents(
 	ctx context.Context, txn *sql.Tx,
-	roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter,
+	roomIDs []string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter,
 	chronologicalOrder bool, onlySyncEvents bool,
-) ([]types.StreamEvent, bool, error) {
+) (map[string]types.RecentEvents, error) {
 	var query string
 	if onlySyncEvents {
 		query = selectRecentEventsForSyncSQL
@@ -378,49 +378,55 @@ func (s *outputRoomEventsStatements) SelectRecentEvents(
 		query = selectRecentEventsSQL
 	}
 
-	stmt, params, err := prepareWithFilters(
-		s.db, txn, query,
-		[]interface{}{
-			roomID, 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)
-	}
-	defer internal.CloseAndLogIfError(ctx, stmt, "selectRecentEvents: stmt.close() failed")
-
-	rows, err := stmt.QueryContext(ctx, params...)
-	if err != nil {
-		return nil, false, err
-	}
-	defer internal.CloseAndLogIfError(ctx, rows, "selectRecentEvents: rows.close() failed")
-	events, err := rowsToStreamEvents(rows)
-	if err != nil {
-		return nil, false, err
-	}
-	if chronologicalOrder {
-		// 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(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 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:]
-		} else {
-			events = events[:len(events)-1]
+	result := make(map[string]types.RecentEvents, len(roomIDs))
+	for _, roomID := range roomIDs {
+		stmt, params, err := prepareWithFilters(
+			s.db, txn, query,
+			[]interface{}{
+				roomID, r.Low(), r.High(),
+			},
+			eventFilter.Senders, eventFilter.NotSenders,
+			eventFilter.Types, eventFilter.NotTypes,
+			nil, eventFilter.ContainsURL, eventFilter.Limit+1, FilterOrderDesc,
+		)
+		if err != nil {
+			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, err
+		}
+		defer internal.CloseAndLogIfError(ctx, rows, "selectRecentEvents: rows.close() failed")
+		events, err := rowsToStreamEvents(rows)
+		if err != nil {
+			return nil, err
+		}
+		if chronologicalOrder {
+			// 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(events, func(i int, j int) bool {
+				return events[i].StreamPosition < events[j].StreamPosition
+			})
+		}
+		res := types.RecentEvents{}
+		// we queried for 1 more than the limit, so if we returned one more mark limited=true
+		if len(events) > eventFilter.Limit {
+			res.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:]
+			} else {
+				events = events[:len(events)-1]
+			}
+		}
+		res.Events = events
+		result[roomID] = res
 	}
-	return events, limited, nil
+
+	return result, nil
 }
 
 func (s *outputRoomEventsStatements) SelectEarlyEvents(