Transactional isolation for /sync (#2745)

This should transactional snapshot isolation for `/sync` etc requests.

For now we don't use repeatable read due to some odd test failures with
invites.

syncapi/storage/shared/storage_consumer.go

@@ -0,0 +1,586 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package shared
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+
+	"github.com/tidwall/gjson"
+
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/sirupsen/logrus"
+
+	"github.com/matrix-org/dendrite/internal/eventutil"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/syncapi/storage/tables"
+	"github.com/matrix-org/dendrite/syncapi/types"
+)
+
+// Database is a temporary struct until we have made syncserver.go the same for both pq/sqlite
+// For now this contains the shared functions
+type Database struct {
+	DB                  *sql.DB
+	Writer              sqlutil.Writer
+	Invites             tables.Invites
+	Peeks               tables.Peeks
+	AccountData         tables.AccountData
+	OutputEvents        tables.Events
+	Topology            tables.Topology
+	CurrentRoomState    tables.CurrentRoomState
+	BackwardExtremities tables.BackwardsExtremities
+	SendToDevice        tables.SendToDevice
+	Filter              tables.Filter
+	Receipts            tables.Receipts
+	Memberships         tables.Memberships
+	NotificationData    tables.NotificationData
+	Ignores             tables.Ignores
+	Presence            tables.Presence
+}
+
+func (d *Database) NewDatabaseSnapshot(ctx context.Context) (*DatabaseTransaction, error) {
+	return d.NewDatabaseTransaction(ctx)
+
+	/*
+		TODO: Repeatable read is probably the right thing to do here,
+		but it seems to cause some problems with the invite tests, so
+		need to investigate that further.
+
+		txn, err := d.DB.BeginTx(ctx, &sql.TxOptions{
+			// Set the isolation level so that we see a snapshot of the database.
+			// In PostgreSQL repeatable read transactions will see a snapshot taken
+			// at the first query, and since the transaction is read-only it can't
+			// run into any serialisation errors.
+			// https://www.postgresql.org/docs/9.5/static/transaction-iso.html#XACT-REPEATABLE-READ
+			Isolation: sql.LevelRepeatableRead,
+			ReadOnly:  true,
+		})
+		if err != nil {
+			return nil, err
+		}
+		return &DatabaseTransaction{
+			Database: d,
+			txn:      txn,
+		}, nil
+	*/
+}
+
+func (d *Database) NewDatabaseTransaction(ctx context.Context) (*DatabaseTransaction, error) {
+	txn, err := d.DB.BeginTx(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+	return &DatabaseTransaction{
+		Database: d,
+		txn:      txn,
+	}, nil
+}
+
+func (d *Database) Events(ctx context.Context, eventIDs []string) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	streamEvents, err := d.OutputEvents.SelectEvents(ctx, nil, eventIDs, nil, false)
+	if err != nil {
+		return nil, err
+	}
+
+	// We don't include a device here as we only include transaction IDs in
+	// incremental syncs.
+	return d.StreamEventsToEvents(nil, streamEvents), nil
+}
+
+// AddInviteEvent stores a new invite event for a user.
+// If the invite was successfully stored this returns the stream ID it was stored at.
+// Returns an error if there was a problem communicating with the database.
+func (d *Database) AddInviteEvent(
+	ctx context.Context, inviteEvent *gomatrixserverlib.HeaderedEvent,
+) (sp types.StreamPosition, err error) {
+	_ = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.Invites.InsertInviteEvent(ctx, txn, inviteEvent)
+		return err
+	})
+	return
+}
+
+// RetireInviteEvent removes an old invite event from the database.
+// Returns an error if there was a problem communicating with the database.
+func (d *Database) RetireInviteEvent(
+	ctx context.Context, inviteEventID string,
+) (sp types.StreamPosition, err error) {
+	_ = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.Invites.DeleteInviteEvent(ctx, txn, inviteEventID)
+		return err
+	})
+	return
+}
+
+// AddPeek tracks the fact that a user has started peeking.
+// If the peek was successfully stored this returns the stream ID it was stored at.
+// Returns an error if there was a problem communicating with the database.
+func (d *Database) AddPeek(
+	ctx context.Context, roomID, userID, deviceID string,
+) (sp types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.Peeks.InsertPeek(ctx, txn, roomID, userID, deviceID)
+		return err
+	})
+	return
+}
+
+// DeletePeek tracks the fact that a user has stopped peeking from the specified
+// device. If the peeks was successfully deleted this returns the stream ID it was
+// stored at. Returns an error if there was a problem communicating with the database.
+func (d *Database) DeletePeek(
+	ctx context.Context, roomID, userID, deviceID string,
+) (sp types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.Peeks.DeletePeek(ctx, txn, roomID, userID, deviceID)
+		return err
+	})
+	if err == sql.ErrNoRows {
+		sp = 0
+		err = nil
+	}
+	return
+}
+
+// DeletePeeks tracks the fact that a user has stopped peeking from all devices
+// If the peeks was successfully deleted this returns the stream ID it was stored at.
+// Returns an error if there was a problem communicating with the database.
+func (d *Database) DeletePeeks(
+	ctx context.Context, roomID, userID string,
+) (sp types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.Peeks.DeletePeeks(ctx, txn, roomID, userID)
+		return err
+	})
+	if err == sql.ErrNoRows {
+		sp = 0
+		err = nil
+	}
+	return
+}
+
+// UpsertAccountData keeps track of new or updated account data, by saving the type
+// of the new/updated data, and the user ID and room ID the data is related to (empty)
+// room ID means the data isn't specific to any room)
+// If no data with the given type, user ID and room ID exists in the database,
+// creates a new row, else update the existing one
+// Returns an error if there was an issue with the upsert
+func (d *Database) UpsertAccountData(
+	ctx context.Context, userID, roomID, dataType string,
+) (sp types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		sp, err = d.AccountData.InsertAccountData(ctx, txn, userID, roomID, dataType)
+		return err
+	})
+	return
+}
+
+func (d *Database) StreamEventsToEvents(device *userapi.Device, in []types.StreamEvent) []*gomatrixserverlib.HeaderedEvent {
+	out := make([]*gomatrixserverlib.HeaderedEvent, len(in))
+	for i := 0; i < len(in); i++ {
+		out[i] = in[i].HeaderedEvent
+		if device != nil && in[i].TransactionID != nil {
+			if device.UserID == in[i].Sender() && device.SessionID == in[i].TransactionID.SessionID {
+				err := out[i].SetUnsignedField(
+					"transaction_id", in[i].TransactionID.TransactionID,
+				)
+				if err != nil {
+					logrus.WithFields(logrus.Fields{
+						"event_id": out[i].EventID(),
+					}).WithError(err).Warnf("Failed to add transaction ID to event")
+				}
+			}
+		}
+	}
+	return out
+}
+
+// handleBackwardExtremities adds this event as a backwards extremity if and only if we do not have all of
+// the events listed in the event's 'prev_events'. This function also updates the backwards extremities table
+// to account for the fact that the given event is no longer a backwards extremity, but may be marked as such.
+// This function should always be called within a sqlutil.Writer for safety in SQLite.
+func (d *Database) handleBackwardExtremities(ctx context.Context, txn *sql.Tx, ev *gomatrixserverlib.HeaderedEvent) error {
+	if err := d.BackwardExtremities.DeleteBackwardExtremity(ctx, txn, ev.RoomID(), ev.EventID()); err != nil {
+		return err
+	}
+
+	// Check if we have all of the event's previous events. If an event is
+	// missing, add it to the room's backward extremities.
+	prevEvents, err := d.OutputEvents.SelectEvents(ctx, txn, ev.PrevEventIDs(), nil, false)
+	if err != nil {
+		return err
+	}
+	var found bool
+	for _, eID := range ev.PrevEventIDs() {
+		found = false
+		for _, prevEv := range prevEvents {
+			if eID == prevEv.EventID() {
+				found = true
+			}
+		}
+
+		// If the event is missing, consider it a backward extremity.
+		if !found {
+			if err = d.BackwardExtremities.InsertsBackwardExtremity(ctx, txn, ev.RoomID(), ev.EventID(), eID); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func (d *Database) PurgeRoomState(
+	ctx context.Context, roomID string,
+) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		// If the event is a create event then we'll delete all of the existing
+		// data for the room. The only reason that a create event would be replayed
+		// to us in this way is if we're about to receive the entire room state.
+		if err := d.CurrentRoomState.DeleteRoomStateForRoom(ctx, txn, roomID); err != nil {
+			return fmt.Errorf("d.CurrentRoomState.DeleteRoomStateForRoom: %w", err)
+		}
+		return nil
+	})
+}
+
+func (d *Database) WriteEvent(
+	ctx context.Context,
+	ev *gomatrixserverlib.HeaderedEvent,
+	addStateEvents []*gomatrixserverlib.HeaderedEvent,
+	addStateEventIDs, removeStateEventIDs []string,
+	transactionID *api.TransactionID, excludeFromSync bool,
+	historyVisibility gomatrixserverlib.HistoryVisibility,
+) (pduPosition types.StreamPosition, returnErr error) {
+	returnErr = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		var err error
+		ev.Visibility = historyVisibility
+		pos, err := d.OutputEvents.InsertEvent(
+			ctx, txn, ev, addStateEventIDs, removeStateEventIDs, transactionID, excludeFromSync, historyVisibility,
+		)
+		if err != nil {
+			return fmt.Errorf("d.OutputEvents.InsertEvent: %w", err)
+		}
+		pduPosition = pos
+		var topoPosition types.StreamPosition
+		if topoPosition, err = d.Topology.InsertEventInTopology(ctx, txn, ev, pos); err != nil {
+			return fmt.Errorf("d.Topology.InsertEventInTopology: %w", err)
+		}
+
+		if err = d.handleBackwardExtremities(ctx, txn, ev); err != nil {
+			return fmt.Errorf("d.handleBackwardExtremities: %w", err)
+		}
+
+		if len(addStateEvents) == 0 && len(removeStateEventIDs) == 0 {
+			// Nothing to do, the event may have just been a message event.
+			return nil
+		}
+		for i := range addStateEvents {
+			addStateEvents[i].Visibility = historyVisibility
+		}
+		return d.updateRoomState(ctx, txn, removeStateEventIDs, addStateEvents, pduPosition, topoPosition)
+	})
+
+	return pduPosition, returnErr
+}
+
+// This function should always be called within a sqlutil.Writer for safety in SQLite.
+func (d *Database) updateRoomState(
+	ctx context.Context, txn *sql.Tx,
+	removedEventIDs []string,
+	addedEvents []*gomatrixserverlib.HeaderedEvent,
+	pduPosition types.StreamPosition,
+	topoPosition types.StreamPosition,
+) error {
+	// remove first, then add, as we do not ever delete state, but do replace state which is a remove followed by an add.
+	for _, eventID := range removedEventIDs {
+		if err := d.CurrentRoomState.DeleteRoomStateByEventID(ctx, txn, eventID); err != nil {
+			return fmt.Errorf("d.CurrentRoomState.DeleteRoomStateByEventID: %w", err)
+		}
+	}
+
+	for _, event := range addedEvents {
+		if event.StateKey() == nil {
+			// ignore non state events
+			continue
+		}
+		var membership *string
+		if event.Type() == "m.room.member" {
+			value, err := event.Membership()
+			if err != nil {
+				return fmt.Errorf("event.Membership: %w", err)
+			}
+			membership = &value
+			if err = d.Memberships.UpsertMembership(ctx, txn, event, pduPosition, topoPosition); err != nil {
+				return fmt.Errorf("d.Memberships.UpsertMembership: %w", err)
+			}
+		}
+
+		if err := d.CurrentRoomState.UpsertRoomState(ctx, txn, event, membership, pduPosition); err != nil {
+			return fmt.Errorf("d.CurrentRoomState.UpsertRoomState: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func (d *Database) GetFilter(
+	ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string,
+) error {
+	return d.Filter.SelectFilter(ctx, nil, target, localpart, filterID)
+}
+
+func (d *Database) PutFilter(
+	ctx context.Context, localpart string, filter *gomatrixserverlib.Filter,
+) (string, error) {
+	var filterID string
+	var err error
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		filterID, err = d.Filter.InsertFilter(ctx, txn, filter, localpart)
+		return err
+	})
+	return filterID, err
+}
+
+func (d *Database) RedactEvent(ctx context.Context, redactedEventID string, redactedBecause *gomatrixserverlib.HeaderedEvent) error {
+	redactedEvents, err := d.Events(ctx, []string{redactedEventID})
+	if err != nil {
+		return err
+	}
+	if len(redactedEvents) == 0 {
+		logrus.WithField("event_id", redactedEventID).WithField("redaction_event", redactedBecause.EventID()).Warnf("missing redacted event for redaction")
+		return nil
+	}
+	eventToRedact := redactedEvents[0].Unwrap()
+	redactionEvent := redactedBecause.Unwrap()
+	if err = eventutil.RedactEvent(redactionEvent, eventToRedact); err != nil {
+		return err
+	}
+
+	newEvent := eventToRedact.Headered(redactedBecause.RoomVersion)
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.OutputEvents.UpdateEventJSON(ctx, txn, newEvent)
+	})
+	return err
+}
+
+// fetchStateEvents converts the set of event IDs into a set of events. It will fetch any which are missing from the database.
+// Returns a map of room ID to list of events.
+func (d *Database) fetchStateEvents(
+	ctx context.Context, txn *sql.Tx,
+	roomIDToEventIDSet map[string]map[string]bool,
+	eventIDToEvent map[string]types.StreamEvent,
+) (map[string][]types.StreamEvent, error) {
+	stateBetween := make(map[string][]types.StreamEvent)
+	missingEvents := make(map[string][]string)
+	for roomID, ids := range roomIDToEventIDSet {
+		events := stateBetween[roomID]
+		for id, need := range ids {
+			if !need {
+				continue // deleted state
+			}
+			e, ok := eventIDToEvent[id]
+			if ok {
+				events = append(events, e)
+			} else {
+				m := missingEvents[roomID]
+				m = append(m, id)
+				missingEvents[roomID] = m
+			}
+		}
+		stateBetween[roomID] = events
+	}
+
+	if len(missingEvents) > 0 {
+		// This happens when add_state_ids has an event ID which is not in the provided range.
+		// We need to explicitly fetch them.
+		allMissingEventIDs := []string{}
+		for _, missingEvIDs := range missingEvents {
+			allMissingEventIDs = append(allMissingEventIDs, missingEvIDs...)
+		}
+		evs, err := d.fetchMissingStateEvents(ctx, txn, allMissingEventIDs)
+		if err != nil {
+			return nil, err
+		}
+		// we know we got them all otherwise an error would've been returned, so just loop the events
+		for _, ev := range evs {
+			roomID := ev.RoomID()
+			stateBetween[roomID] = append(stateBetween[roomID], ev)
+		}
+	}
+	return stateBetween, nil
+}
+
+func (d *Database) fetchMissingStateEvents(
+	ctx context.Context, txn *sql.Tx, eventIDs []string,
+) ([]types.StreamEvent, error) {
+	// Fetch from the events table first so we pick up the stream ID for the
+	// event.
+	events, err := d.OutputEvents.SelectEvents(ctx, txn, eventIDs, nil, false)
+	if err != nil {
+		return nil, err
+	}
+
+	have := map[string]bool{}
+	for _, event := range events {
+		have[event.EventID()] = true
+	}
+	var missing []string
+	for _, eventID := range eventIDs {
+		if !have[eventID] {
+			missing = append(missing, eventID)
+		}
+	}
+	if len(missing) == 0 {
+		return events, nil
+	}
+
+	// If they are missing from the events table then they should be state
+	// events that we received from outside the main event stream.
+	// These should be in the room state table.
+	stateEvents, err := d.CurrentRoomState.SelectEventsWithEventIDs(ctx, txn, missing)
+
+	if err != nil {
+		return nil, err
+	}
+	if len(stateEvents) != len(missing) {
+		logrus.WithContext(ctx).Warnf("Failed to map all event IDs to events (got %d, wanted %d)", len(stateEvents), len(missing))
+
+		// TODO: Why is this happening? It's probably the roomserver. Uncomment
+		// this error again when we work out what it is and fix it, otherwise we
+		// just end up returning lots of 500s to the client and that breaks
+		// pretty much everything, rather than just sending what we have.
+		//return nil, fmt.Errorf("failed to map all event IDs to events: (got %d, wanted %d)", len(stateEvents), len(missing))
+	}
+	events = append(events, stateEvents...)
+	return events, nil
+}
+
+func (d *Database) StoreNewSendForDeviceMessage(
+	ctx context.Context, userID, deviceID string, event gomatrixserverlib.SendToDeviceEvent,
+) (newPos types.StreamPosition, err error) {
+	j, err := json.Marshal(event)
+	if err != nil {
+		return 0, err
+	}
+	// Delegate the database write task to the SendToDeviceWriter. It'll guarantee
+	// that we don't lock the table for writes in more than one place.
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		newPos, err = d.SendToDevice.InsertSendToDeviceMessage(
+			ctx, txn, userID, deviceID, string(j),
+		)
+		return err
+	})
+	if err != nil {
+		return 0, err
+	}
+	return newPos, nil
+}
+
+func (d *Database) CleanSendToDeviceUpdates(
+	ctx context.Context,
+	userID, deviceID string, before types.StreamPosition,
+) (err error) {
+	if err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.SendToDevice.DeleteSendToDeviceMessages(ctx, txn, userID, deviceID, before)
+	}); err != nil {
+		logrus.WithError(err).Errorf("Failed to clean up old send-to-device messages for user %q device %q", userID, deviceID)
+		return err
+	}
+	return nil
+}
+
+// getMembershipFromEvent returns the value of content.membership iff the event is a state event
+// with type 'm.room.member' and state_key of userID. Otherwise, an empty string is returned.
+func getMembershipFromEvent(ev *gomatrixserverlib.Event, userID string) (string, string) {
+	if ev.Type() != "m.room.member" || !ev.StateKeyEquals(userID) {
+		return "", ""
+	}
+	membership, err := ev.Membership()
+	if err != nil {
+		return "", ""
+	}
+	prevMembership := gjson.GetBytes(ev.Unsigned(), "prev_content.membership").Str
+	return membership, prevMembership
+}
+
+// StoreReceipt stores user receipts
+func (d *Database) StoreReceipt(ctx context.Context, roomId, receiptType, userId, eventId string, timestamp gomatrixserverlib.Timestamp) (pos types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		pos, err = d.Receipts.UpsertReceipt(ctx, txn, roomId, receiptType, userId, eventId, timestamp)
+		return err
+	})
+	return
+}
+
+func (d *Database) UpsertRoomUnreadNotificationCounts(ctx context.Context, userID, roomID string, notificationCount, highlightCount int) (pos types.StreamPosition, err error) {
+	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		pos, err = d.NotificationData.UpsertRoomUnreadCounts(ctx, txn, userID, roomID, notificationCount, highlightCount)
+		return err
+	})
+	return
+}
+
+func (d *Database) SelectContextEvent(ctx context.Context, roomID, eventID string) (int, gomatrixserverlib.HeaderedEvent, error) {
+	return d.OutputEvents.SelectContextEvent(ctx, nil, roomID, eventID)
+}
+
+func (d *Database) SelectContextBeforeEvent(ctx context.Context, id int, roomID string, filter *gomatrixserverlib.RoomEventFilter) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	return d.OutputEvents.SelectContextBeforeEvent(ctx, nil, id, roomID, filter)
+}
+func (d *Database) SelectContextAfterEvent(ctx context.Context, id int, roomID string, filter *gomatrixserverlib.RoomEventFilter) (int, []*gomatrixserverlib.HeaderedEvent, error) {
+	return d.OutputEvents.SelectContextAfterEvent(ctx, nil, id, roomID, filter)
+}
+
+func (d *Database) IgnoresForUser(ctx context.Context, userID string) (*types.IgnoredUsers, error) {
+	return d.Ignores.SelectIgnores(ctx, nil, userID)
+}
+
+func (d *Database) UpdateIgnoresForUser(ctx context.Context, userID string, ignores *types.IgnoredUsers) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.Ignores.UpsertIgnores(ctx, txn, userID, ignores)
+	})
+}
+
+func (d *Database) UpdatePresence(ctx context.Context, userID string, presence types.Presence, statusMsg *string, lastActiveTS gomatrixserverlib.Timestamp, fromSync bool) (types.StreamPosition, error) {
+	var pos types.StreamPosition
+	var err error
+	_ = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		pos, err = d.Presence.UpsertPresence(ctx, txn, userID, statusMsg, presence, lastActiveTS, fromSync)
+		return nil
+	})
+	return pos, err
+}
+
+func (d *Database) GetPresence(ctx context.Context, userID string) (*types.PresenceInternal, error) {
+	return d.Presence.GetPresenceForUser(ctx, nil, userID)
+}
+
+func (d *Database) SelectMembershipForUser(ctx context.Context, roomID, userID string, pos int64) (membership string, topologicalPos int, err error) {
+	return d.Memberships.SelectMembershipForUser(ctx, nil, roomID, userID, pos)
+}
+
+func (s *Database) ReIndex(ctx context.Context, limit, afterID int64) (map[int64]gomatrixserverlib.HeaderedEvent, error) {
+	return s.OutputEvents.ReIndex(ctx, nil, limit, afterID, []string{
+		gomatrixserverlib.MRoomName,
+		gomatrixserverlib.MRoomTopic,
+		"m.room.message",
+	})
+}

syncapi/storage/shared/storage_sync.go

@@ -0,0 +1,574 @@
+package shared
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/matrix-org/dendrite/internal/eventutil"
+	"github.com/matrix-org/dendrite/syncapi/types"
+	userapi "github.com/matrix-org/dendrite/userapi/api"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+type DatabaseTransaction struct {
+	*Database
+	txn *sql.Tx
+}
+
+func (d *DatabaseTransaction) Commit() error {
+	if d.txn == nil {
+		return nil
+	}
+	return d.txn.Commit()
+}
+
+func (d *DatabaseTransaction) Rollback() error {
+	if d.txn == nil {
+		return nil
+	}
+	return d.txn.Rollback()
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForPDUs(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.OutputEvents.SelectMaxEventID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.OutputEvents.SelectMaxEventID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForReceipts(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.Receipts.SelectMaxReceiptID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.Receipts.SelectMaxReceiptID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForInvites(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.Invites.SelectMaxInviteID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.Invites.SelectMaxInviteID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForSendToDeviceMessages(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.SendToDevice.SelectMaxSendToDeviceMessageID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.SendToDevice.SelectMaxSendToDeviceMessageID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForAccountData(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.AccountData.SelectMaxAccountDataID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.Invites.SelectMaxAccountDataID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForNotificationData(ctx context.Context) (types.StreamPosition, error) {
+	id, err := d.NotificationData.SelectMaxID(ctx, d.txn)
+	if err != nil {
+		return 0, fmt.Errorf("d.NotificationData.SelectMaxID: %w", err)
+	}
+	return types.StreamPosition(id), nil
+}
+
+func (d *DatabaseTransaction) CurrentState(ctx context.Context, roomID string, stateFilterPart *gomatrixserverlib.StateFilter, excludeEventIDs []string) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	return d.CurrentRoomState.SelectCurrentState(ctx, d.txn, roomID, stateFilterPart, excludeEventIDs)
+}
+
+func (d *DatabaseTransaction) RoomIDsWithMembership(ctx context.Context, userID string, membership string) ([]string, error) {
+	return d.CurrentRoomState.SelectRoomIDsWithMembership(ctx, d.txn, userID, membership)
+}
+
+func (d *DatabaseTransaction) MembershipCount(ctx context.Context, roomID, membership string, pos types.StreamPosition) (int, error) {
+	return d.Memberships.SelectMembershipCount(ctx, d.txn, roomID, membership, pos)
+}
+
+func (d *DatabaseTransaction) GetRoomHeroes(ctx context.Context, roomID, userID string, memberships []string) ([]string, error) {
+	return d.Memberships.SelectHeroes(ctx, d.txn, roomID, userID, memberships)
+}
+
+func (d *DatabaseTransaction) RecentEvents(ctx context.Context, roomID string, r types.Range, eventFilter *gomatrixserverlib.RoomEventFilter, chronologicalOrder bool, onlySyncEvents bool) ([]types.StreamEvent, bool, error) {
+	return d.OutputEvents.SelectRecentEvents(ctx, d.txn, roomID, r, eventFilter, chronologicalOrder, onlySyncEvents)
+}
+
+func (d *DatabaseTransaction) PositionInTopology(ctx context.Context, eventID string) (pos types.StreamPosition, spos types.StreamPosition, err error) {
+	return d.Topology.SelectPositionInTopology(ctx, d.txn, eventID)
+}
+
+func (d *DatabaseTransaction) InviteEventsInRange(ctx context.Context, targetUserID string, r types.Range) (map[string]*gomatrixserverlib.HeaderedEvent, map[string]*gomatrixserverlib.HeaderedEvent, types.StreamPosition, error) {
+	return d.Invites.SelectInviteEventsInRange(ctx, d.txn, targetUserID, r)
+}
+
+func (d *DatabaseTransaction) PeeksInRange(ctx context.Context, userID, deviceID string, r types.Range) (peeks []types.Peek, err error) {
+	return d.Peeks.SelectPeeksInRange(ctx, d.txn, userID, deviceID, r)
+}
+
+func (d *DatabaseTransaction) RoomReceiptsAfter(ctx context.Context, roomIDs []string, streamPos types.StreamPosition) (types.StreamPosition, []types.OutputReceiptEvent, error) {
+	return d.Receipts.SelectRoomReceiptsAfter(ctx, d.txn, roomIDs, streamPos)
+}
+
+// Events lookups a list of event by their event ID.
+// Returns a list of events matching the requested IDs found in the database.
+// If an event is not found in the database then it will be omitted from the list.
+// Returns an error if there was a problem talking with the database.
+// Does not include any transaction IDs in the returned events.
+func (d *DatabaseTransaction) Events(ctx context.Context, eventIDs []string) ([]*gomatrixserverlib.HeaderedEvent, error) {
+	streamEvents, err := d.OutputEvents.SelectEvents(ctx, d.txn, eventIDs, nil, false)
+	if err != nil {
+		return nil, err
+	}
+
+	// We don't include a device here as we only include transaction IDs in
+	// incremental syncs.
+	return d.StreamEventsToEvents(nil, streamEvents), nil
+}
+
+func (d *DatabaseTransaction) AllJoinedUsersInRooms(ctx context.Context) (map[string][]string, error) {
+	return d.CurrentRoomState.SelectJoinedUsers(ctx, d.txn)
+}
+
+func (d *DatabaseTransaction) AllJoinedUsersInRoom(ctx context.Context, roomIDs []string) (map[string][]string, error) {
+	return d.CurrentRoomState.SelectJoinedUsersInRoom(ctx, d.txn, roomIDs)
+}
+
+func (d *DatabaseTransaction) AllPeekingDevicesInRooms(ctx context.Context) (map[string][]types.PeekingDevice, error) {
+	return d.Peeks.SelectPeekingDevices(ctx, d.txn)
+}
+
+func (d *DatabaseTransaction) SharedUsers(ctx context.Context, userID string, otherUserIDs []string) ([]string, error) {
+	return d.CurrentRoomState.SelectSharedUsers(ctx, d.txn, userID, otherUserIDs)
+}
+
+func (d *DatabaseTransaction) GetStateEvent(
+	ctx context.Context, roomID, evType, stateKey string,
+) (*gomatrixserverlib.HeaderedEvent, error) {
+	return d.CurrentRoomState.SelectStateEvent(ctx, d.txn, roomID, evType, stateKey)
+}
+
+func (d *DatabaseTransaction) GetStateEventsForRoom(
+	ctx context.Context, roomID string, stateFilter *gomatrixserverlib.StateFilter,
+) (stateEvents []*gomatrixserverlib.HeaderedEvent, err error) {
+	stateEvents, err = d.CurrentRoomState.SelectCurrentState(ctx, d.txn, roomID, stateFilter, nil)
+	return
+}
+
+// GetAccountDataInRange returns all account data for a given user inserted or
+// updated between two given positions
+// Returns a map following the format data[roomID] = []dataTypes
+// If no data is retrieved, returns an empty map
+// If there was an issue with the retrieval, returns an error
+func (d *DatabaseTransaction) GetAccountDataInRange(
+	ctx context.Context, userID string, r types.Range,
+	accountDataFilterPart *gomatrixserverlib.EventFilter,
+) (map[string][]string, types.StreamPosition, error) {
+	return d.AccountData.SelectAccountDataInRange(ctx, d.txn, userID, r, accountDataFilterPart)
+}
+
+func (d *DatabaseTransaction) GetEventsInTopologicalRange(
+	ctx context.Context,
+	from, to *types.TopologyToken,
+	roomID string,
+	filter *gomatrixserverlib.RoomEventFilter,
+	backwardOrdering bool,
+) (events []types.StreamEvent, err error) {
+	var minDepth, maxDepth, maxStreamPosForMaxDepth types.StreamPosition
+	if backwardOrdering {
+		// Backward ordering means the 'from' token has a higher depth than the 'to' token
+		minDepth = to.Depth
+		maxDepth = from.Depth
+		// for cases where we have say 5 events with the same depth, the TopologyToken needs to
+		// know which of the 5 the client has seen. This is done by using the PDU position.
+		// Events with the same maxDepth but less than this PDU position will be returned.
+		maxStreamPosForMaxDepth = from.PDUPosition
+	} else {
+		// Forward ordering means the 'from' token has a lower depth than the 'to' token.
+		minDepth = from.Depth
+		maxDepth = to.Depth
+	}
+
+	// Select the event IDs from the defined range.
+	var eIDs []string
+	eIDs, err = d.Topology.SelectEventIDsInRange(
+		ctx, d.txn, roomID, minDepth, maxDepth, maxStreamPosForMaxDepth, filter.Limit, !backwardOrdering,
+	)
+	if err != nil {
+		return
+	}
+
+	// Retrieve the events' contents using their IDs.
+	events, err = d.OutputEvents.SelectEvents(ctx, d.txn, eIDs, filter, true)
+	return
+}
+
+func (d *DatabaseTransaction) BackwardExtremitiesForRoom(
+	ctx context.Context, roomID string,
+) (backwardExtremities map[string][]string, err error) {
+	return d.BackwardExtremities.SelectBackwardExtremitiesForRoom(ctx, d.txn, roomID)
+}
+
+func (d *DatabaseTransaction) MaxTopologicalPosition(
+	ctx context.Context, roomID string,
+) (types.TopologyToken, error) {
+	depth, streamPos, err := d.Topology.SelectMaxPositionInTopology(ctx, d.txn, roomID)
+	if err != nil {
+		return types.TopologyToken{}, err
+	}
+	return types.TopologyToken{Depth: depth, PDUPosition: streamPos}, nil
+}
+
+func (d *DatabaseTransaction) EventPositionInTopology(
+	ctx context.Context, eventID string,
+) (types.TopologyToken, error) {
+	depth, stream, err := d.Topology.SelectPositionInTopology(ctx, d.txn, eventID)
+	if err != nil {
+		return types.TopologyToken{}, err
+	}
+	return types.TopologyToken{Depth: depth, PDUPosition: stream}, nil
+}
+
+func (d *DatabaseTransaction) StreamToTopologicalPosition(
+	ctx context.Context, roomID string, streamPos types.StreamPosition, backwardOrdering bool,
+) (types.TopologyToken, error) {
+	topoPos, err := d.Topology.SelectStreamToTopologicalPosition(ctx, d.txn, roomID, streamPos, backwardOrdering)
+	switch {
+	case err == sql.ErrNoRows && backwardOrdering: // no events in range, going backward
+		return types.TopologyToken{PDUPosition: streamPos}, nil
+	case err == sql.ErrNoRows && !backwardOrdering: // no events in range, going forward
+		topoPos, streamPos, err = d.Topology.SelectMaxPositionInTopology(ctx, d.txn, roomID)
+		if err != nil {
+			return types.TopologyToken{}, fmt.Errorf("d.Topology.SelectMaxPositionInTopology: %w", err)
+		}
+		return types.TopologyToken{Depth: topoPos, PDUPosition: streamPos}, nil
+	case err != nil: // some other error happened
+		return types.TopologyToken{}, fmt.Errorf("d.Topology.SelectStreamToTopologicalPosition: %w", err)
+	default:
+		return types.TopologyToken{Depth: topoPos, PDUPosition: streamPos}, nil
+	}
+}
+
+// GetBackwardTopologyPos retrieves the backward topology position, i.e. the position of the
+// oldest event in the room's topology.
+func (d *DatabaseTransaction) GetBackwardTopologyPos(
+	ctx context.Context,
+	events []types.StreamEvent,
+) (types.TopologyToken, error) {
+	zeroToken := types.TopologyToken{}
+	if len(events) == 0 {
+		return zeroToken, nil
+	}
+	pos, spos, err := d.Topology.SelectPositionInTopology(ctx, d.txn, events[0].EventID())
+	if err != nil {
+		return zeroToken, err
+	}
+	tok := types.TopologyToken{Depth: pos, PDUPosition: spos}
+	tok.Decrement()
+	return tok, nil
+}
+
+// GetStateDeltas returns the state deltas between fromPos and toPos,
+// exclusive of oldPos, inclusive of newPos, for the rooms in which
+// the user has new membership events.
+// A list of joined room IDs is also returned in case the caller needs it.
+func (d *DatabaseTransaction) GetStateDeltas(
+	ctx context.Context, device *userapi.Device,
+	r types.Range, userID string,
+	stateFilter *gomatrixserverlib.StateFilter,
+) (deltas []types.StateDelta, joinedRoomsIDs []string, err error) {
+	// Implement membership change algorithm: https://github.com/matrix-org/synapse/blob/v0.19.3/synapse/handlers/sync.py#L821
+	// - Get membership list changes for this user in this sync response
+	// - For each room which has membership list changes:
+	//     * Check if the room is 'newly joined' (insufficient to just check for a join event because we allow dupe joins TODO).
+	//       If it is, then we need to send the full room state down (and 'limited' is always true).
+	//     * Check if user is still CURRENTLY invited to the room. If so, add room to 'invited' block.
+	//     * Check if the user is CURRENTLY (TODO) left/banned. If so, add room to 'archived' block.
+	// - Get all CURRENTLY joined rooms, and add them to 'joined' block.
+
+	// Look up all memberships for the user. We only care about rooms that a
+	// user has ever interacted with — joined to, kicked/banned from, left.
+	memberships, err := d.CurrentRoomState.SelectRoomIDsWithAnyMembership(ctx, d.txn, userID)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil, nil
+		}
+		return nil, nil, err
+	}
+
+	allRoomIDs := make([]string, 0, len(memberships))
+	joinedRoomIDs := make([]string, 0, len(memberships))
+	for roomID, membership := range memberships {
+		allRoomIDs = append(allRoomIDs, roomID)
+		if membership == gomatrixserverlib.Join {
+			joinedRoomIDs = append(joinedRoomIDs, roomID)
+		}
+	}
+
+	// get all the state events ever (i.e. for all available rooms) between these two positions
+	stateNeeded, eventMap, 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
+	}
+	state, err := d.fetchStateEvents(ctx, d.txn, stateNeeded, eventMap)
+	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
+	peeks, err := d.Peeks.SelectPeeksInRange(ctx, d.txn, userID, device.ID, r)
+	if err != nil && err != sql.ErrNoRows {
+		return nil, nil, err
+	}
+
+	// add peek blocks
+	for _, peek := range peeks {
+		if peek.New {
+			// send full room state down instead of a delta
+			var s []types.StreamEvent
+			s, err = d.currentStateStreamEventsForRoom(ctx, peek.RoomID, stateFilter)
+			if err != nil {
+				if err == sql.ErrNoRows {
+					continue
+				}
+				return nil, nil, err
+			}
+			state[peek.RoomID] = s
+		}
+		if !peek.Deleted {
+			deltas = append(deltas, types.StateDelta{
+				Membership:  gomatrixserverlib.Peek,
+				StateEvents: d.StreamEventsToEvents(device, state[peek.RoomID]),
+				RoomID:      peek.RoomID,
+			})
+		}
+	}
+
+	// handle newly joined rooms and non-joined rooms
+	newlyJoinedRooms := make(map[string]bool, len(state))
+	for roomID, stateStreamEvents := range state {
+		for _, ev := range stateStreamEvents {
+			if membership, prevMembership := getMembershipFromEvent(ev.Event, userID); membership != "" {
+				if membership == gomatrixserverlib.Join && prevMembership != membership {
+					// send full room state down instead of a delta
+					var s []types.StreamEvent
+					s, err = d.currentStateStreamEventsForRoom(ctx, roomID, stateFilter)
+					if err != nil {
+						if err == sql.ErrNoRows {
+							continue
+						}
+						return nil, nil, err
+					}
+					state[roomID] = s
+					newlyJoinedRooms[roomID] = true
+					continue // we'll add this room in when we do joined rooms
+				}
+
+				deltas = append(deltas, types.StateDelta{
+					Membership:    membership,
+					MembershipPos: ev.StreamPosition,
+					StateEvents:   d.StreamEventsToEvents(device, stateStreamEvents),
+					RoomID:        roomID,
+				})
+				break
+			}
+		}
+	}
+
+	// Add in currently joined rooms
+	for _, joinedRoomID := range joinedRoomIDs {
+		deltas = append(deltas, types.StateDelta{
+			Membership:  gomatrixserverlib.Join,
+			StateEvents: d.StreamEventsToEvents(device, state[joinedRoomID]),
+			RoomID:      joinedRoomID,
+			NewlyJoined: newlyJoinedRooms[joinedRoomID],
+		})
+	}
+
+	return deltas, joinedRoomIDs, nil
+}
+
+// GetStateDeltasForFullStateSync is a variant of getStateDeltas used for /sync
+// requests with full_state=true.
+// Fetches full state for all joined rooms and uses selectStateInRange to get
+// updates for other rooms.
+func (d *DatabaseTransaction) GetStateDeltasForFullStateSync(
+	ctx context.Context, device *userapi.Device,
+	r types.Range, userID string,
+	stateFilter *gomatrixserverlib.StateFilter,
+) ([]types.StateDelta, []string, error) {
+	// Look up all memberships for the user. We only care about rooms that a
+	// user has ever interacted with — joined to, kicked/banned from, left.
+	memberships, err := d.CurrentRoomState.SelectRoomIDsWithAnyMembership(ctx, d.txn, userID)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil, nil
+		}
+		return nil, nil, err
+	}
+
+	allRoomIDs := make([]string, 0, len(memberships))
+	joinedRoomIDs := make([]string, 0, len(memberships))
+	for roomID, membership := range memberships {
+		allRoomIDs = append(allRoomIDs, roomID)
+		if membership == gomatrixserverlib.Join {
+			joinedRoomIDs = append(joinedRoomIDs, roomID)
+		}
+	}
+
+	// Use a reasonable initial capacity
+	deltas := make(map[string]types.StateDelta)
+
+	peeks, err := d.Peeks.SelectPeeksInRange(ctx, d.txn, userID, device.ID, r)
+	if err != nil && err != sql.ErrNoRows {
+		return nil, nil, err
+	}
+
+	// Add full states for all peeking rooms
+	for _, peek := range peeks {
+		if !peek.Deleted {
+			s, stateErr := d.currentStateStreamEventsForRoom(ctx, peek.RoomID, stateFilter)
+			if stateErr != nil {
+				if stateErr == sql.ErrNoRows {
+					continue
+				}
+				return nil, nil, stateErr
+			}
+			deltas[peek.RoomID] = types.StateDelta{
+				Membership:  gomatrixserverlib.Peek,
+				StateEvents: d.StreamEventsToEvents(device, s),
+				RoomID:      peek.RoomID,
+			}
+		}
+	}
+
+	// Get all the state events ever between these two positions
+	stateNeeded, eventMap, 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
+	}
+	state, err := d.fetchStateEvents(ctx, d.txn, stateNeeded, eventMap)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil, nil
+		}
+		return nil, nil, err
+	}
+
+	for roomID, stateStreamEvents := range state {
+		for _, ev := range stateStreamEvents {
+			if membership, _ := getMembershipFromEvent(ev.Event, userID); membership != "" {
+				if membership != gomatrixserverlib.Join { // We've already added full state for all joined rooms above.
+					deltas[roomID] = types.StateDelta{
+						Membership:    membership,
+						MembershipPos: ev.StreamPosition,
+						StateEvents:   d.StreamEventsToEvents(device, stateStreamEvents),
+						RoomID:        roomID,
+					}
+				}
+
+				break
+			}
+		}
+	}
+
+	// Add full states for all joined rooms
+	for _, joinedRoomID := range joinedRoomIDs {
+		s, stateErr := d.currentStateStreamEventsForRoom(ctx, joinedRoomID, stateFilter)
+		if stateErr != nil {
+			if stateErr == sql.ErrNoRows {
+				continue
+			}
+			return nil, nil, stateErr
+		}
+		deltas[joinedRoomID] = types.StateDelta{
+			Membership:  gomatrixserverlib.Join,
+			StateEvents: d.StreamEventsToEvents(device, s),
+			RoomID:      joinedRoomID,
+		}
+	}
+
+	// Create a response array.
+	result := make([]types.StateDelta, len(deltas))
+	i := 0
+	for _, delta := range deltas {
+		result[i] = delta
+		i++
+	}
+
+	return result, joinedRoomIDs, nil
+}
+
+func (d *DatabaseTransaction) currentStateStreamEventsForRoom(
+	ctx context.Context, roomID string,
+	stateFilter *gomatrixserverlib.StateFilter,
+) ([]types.StreamEvent, error) {
+	allState, err := d.CurrentRoomState.SelectCurrentState(ctx, d.txn, roomID, stateFilter, nil)
+	if err != nil {
+		return nil, err
+	}
+	s := make([]types.StreamEvent, len(allState))
+	for i := 0; i < len(s); i++ {
+		s[i] = types.StreamEvent{HeaderedEvent: allState[i], StreamPosition: 0}
+	}
+	return s, nil
+}
+
+func (d *DatabaseTransaction) SendToDeviceUpdatesForSync(
+	ctx context.Context,
+	userID, deviceID string,
+	from, to types.StreamPosition,
+) (types.StreamPosition, []types.SendToDeviceEvent, error) {
+	// First of all, get our send-to-device updates for this user.
+	lastPos, events, err := d.SendToDevice.SelectSendToDeviceMessages(ctx, d.txn, userID, deviceID, from, to)
+	if err != nil {
+		return from, nil, fmt.Errorf("d.SendToDevice.SelectSendToDeviceMessages: %w", err)
+	}
+	// If there's nothing to do then stop here.
+	if len(events) == 0 {
+		return to, nil, nil
+	}
+	return lastPos, events, nil
+}
+
+func (d *DatabaseTransaction) GetRoomReceipts(ctx context.Context, roomIDs []string, streamPos types.StreamPosition) ([]types.OutputReceiptEvent, error) {
+	_, receipts, err := d.Receipts.SelectRoomReceiptsAfter(ctx, d.txn, roomIDs, streamPos)
+	return receipts, err
+}
+
+func (d *DatabaseTransaction) GetUserUnreadNotificationCountsForRooms(ctx context.Context, userID string, rooms map[string]string) (map[string]*eventutil.NotificationData, error) {
+	roomIDs := make([]string, 0, len(rooms))
+	for roomID, membership := range rooms {
+		if membership != gomatrixserverlib.Join {
+			continue
+		}
+		roomIDs = append(roomIDs, roomID)
+	}
+	return d.NotificationData.SelectUserUnreadCountsForRooms(ctx, d.txn, userID, roomIDs)
+}
+
+func (d *DatabaseTransaction) GetPresence(ctx context.Context, userID string) (*types.PresenceInternal, error) {
+	return d.Presence.GetPresenceForUser(ctx, d.txn, userID)
+}
+
+func (d *DatabaseTransaction) PresenceAfter(ctx context.Context, after types.StreamPosition, filter gomatrixserverlib.EventFilter) (map[string]*types.PresenceInternal, error) {
+	return d.Presence.GetPresenceAfter(ctx, d.txn, after, filter)
+}
+
+func (d *DatabaseTransaction) MaxStreamPositionForPresence(ctx context.Context) (types.StreamPosition, error) {
+	return d.Presence.GetMaxPresenceID(ctx, d.txn)
+}