Don't leak timeline after leaving room

syncapi/storage/interface.go

@@ -49,6 +49,9 @@ type Database interface {
 	PeeksInRange(ctx context.Context, userID, deviceID string, r types.Range) (peeks []types.Peek, err error)
 	RoomReceiptsAfter(ctx context.Context, roomIDs []string, streamPos types.StreamPosition) (types.StreamPosition, []eduAPI.OutputReceiptEvent, error)
 
+	// MostRecentMembership returns the most recent membership event for the user, along with the global stream position.
+	MostRecentMembership(ctx context.Context, roomID, userID string) (*gomatrixserverlib.HeaderedEvent, types.StreamPosition, error)
+
 	// AllJoinedUsersInRooms returns a map of room ID to a list of all joined user IDs.
 	AllJoinedUsersInRooms(ctx context.Context) (map[string][]string, error)
 	// AllPeekingDevicesInRooms returns a map of room ID to a list of all peeking devices.

syncapi/storage/postgres/output_room_events_table.go

@@ -130,6 +130,10 @@ const selectStateInRangeSQL = "" +
 const deleteEventsForRoomSQL = "" +
 	"DELETE FROM syncapi_output_room_events WHERE room_id = $1"
 
+const selectPositionInStreamSQL = "" +
+	"SELECT id FROM syncapi_output_room_events" +
+	" WHERE event_id = $1"
+
 type outputRoomEventsStatements struct {
 	insertEventStmt               *sql.Stmt
 	selectEventsStmt              *sql.Stmt
@@ -140,6 +144,7 @@ type outputRoomEventsStatements struct {
 	selectStateInRangeStmt        *sql.Stmt
 	updateEventJSONStmt           *sql.Stmt
 	deleteEventsForRoomStmt       *sql.Stmt
+	selectPositionInStreamStmt    *sql.Stmt
 }
 
 func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
@@ -175,6 +180,9 @@ func NewPostgresEventsTable(db *sql.DB) (tables.Events, error) {
 	if s.deleteEventsForRoomStmt, err = db.Prepare(deleteEventsForRoomSQL); err != nil {
 		return nil, err
 	}
+	if s.selectPositionInStreamStmt, err = db.Prepare(selectPositionInStreamSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -435,6 +443,15 @@ func (s *outputRoomEventsStatements) DeleteEventsForRoom(
 	return err
 }
 
+// SelectPositionInStream returns the position of a given event in the
+// global stream topology.
+func (s *outputRoomEventsStatements) SelectPositionInStream(
+	ctx context.Context, txn *sql.Tx, eventID string,
+) (pos types.StreamPosition, err error) {
+	err = s.selectPositionInStreamStmt.QueryRowContext(ctx, eventID).Scan(&pos)
+	return
+}
+
 func rowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
 	var result []types.StreamEvent
 	for rows.Next() {

syncapi/storage/shared/syncserver.go

@@ -500,6 +500,20 @@ func (d *Database) EventPositionInTopology(
 	return types.TopologyToken{Depth: depth, PDUPosition: stream}, nil
 }
 
+func (d *Database) MostRecentMembership(
+	ctx context.Context, roomID, userID string,
+) (*gomatrixserverlib.HeaderedEvent, types.StreamPosition, error) {
+	event, err := d.CurrentRoomState.SelectStateEvent(ctx, roomID, gomatrixserverlib.MRoomMember, userID)
+	if err != nil {
+		return nil, 0, fmt.Errorf("d.CurrentRoomState.SelectStateEvent: %w", err)
+	}
+	pos, err := d.OutputEvents.SelectPositionInStream(ctx, nil, event.EventID())
+	if err != nil {
+		return nil, 0, fmt.Errorf("d.OutputEvents.SelectPositionInStream: %w", err)
+	}
+	return event, pos, nil
+}
+
 func (d *Database) GetFilter(
 	ctx context.Context, localpart string, filterID string,
 ) (*gomatrixserverlib.Filter, error) {

syncapi/storage/sqlite3/output_room_events_table.go

@@ -90,14 +90,19 @@ const selectStateInRangeSQL = "" +
 const deleteEventsForRoomSQL = "" +
 	"DELETE FROM syncapi_output_room_events WHERE room_id = $1"
 
+const selectPositionInStreamSQL = "" +
+	"SELECT id FROM syncapi_output_room_events" +
+	" WHERE event_id = $1"
+
 type outputRoomEventsStatements struct {
-	db                      *sql.DB
-	streamIDStatements      *streamIDStatements
-	insertEventStmt         *sql.Stmt
-	selectEventsStmt        *sql.Stmt
-	selectMaxEventIDStmt    *sql.Stmt
-	updateEventJSONStmt     *sql.Stmt
-	deleteEventsForRoomStmt *sql.Stmt
+	db                         *sql.DB
+	streamIDStatements         *streamIDStatements
+	insertEventStmt            *sql.Stmt
+	selectEventsStmt           *sql.Stmt
+	selectMaxEventIDStmt       *sql.Stmt
+	updateEventJSONStmt        *sql.Stmt
+	deleteEventsForRoomStmt    *sql.Stmt
+	selectPositionInStreamStmt *sql.Stmt
 }
 
 func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Events, error) {
@@ -124,6 +129,9 @@ func NewSqliteEventsTable(db *sql.DB, streamID *streamIDStatements) (tables.Even
 	if s.deleteEventsForRoomStmt, err = db.Prepare(deleteEventsForRoomSQL); err != nil {
 		return nil, err
 	}
+	if s.selectPositionInStreamStmt, err = db.Prepare(selectPositionInStreamSQL); err != nil {
+		return nil, err
+	}
 	return s, nil
 }
 
@@ -424,6 +432,15 @@ func (s *outputRoomEventsStatements) DeleteEventsForRoom(
 	return err
 }
 
+// SelectPositionInStream returns the position of a given event in the
+// global stream topology.
+func (s *outputRoomEventsStatements) SelectPositionInStream(
+	ctx context.Context, txn *sql.Tx, eventID string,
+) (pos types.StreamPosition, err error) {
+	err = s.selectPositionInStreamStmt.QueryRowContext(ctx, eventID).Scan(&pos)
+	return
+}
+
 func rowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
 	var result []types.StreamEvent
 	for rows.Next() {

syncapi/storage/tables/interface.go

@@ -63,6 +63,7 @@ type Events interface {
 	UpdateEventJSON(ctx context.Context, event *gomatrixserverlib.HeaderedEvent) error
 	// DeleteEventsForRoom removes all event information for a room. This should only be done when removing the room entirely.
 	DeleteEventsForRoom(ctx context.Context, txn *sql.Tx, roomID string) (err error)
+	SelectPositionInStream(ctx context.Context, txn *sql.Tx, eventID string) (pos types.StreamPosition, err error)
 }
 
 // Topology keeps track of the depths and stream positions for all events.