Fix prev_batch tokens (#999)

syncapi/storage/postgres/output_room_events_table.go

@@ -94,9 +94,6 @@ const selectEarlyEventsSQL = "" +
 	" WHERE room_id = $1 AND id > $2 AND id <= $3" +
 	" ORDER BY id ASC LIMIT $4"
 
-const selectStreamPositionForEventIDSQL = "" +
-	"SELECT id FROM syncapi_output_room_events WHERE event_id = $1"
-
 const selectMaxEventIDSQL = "" +
 	"SELECT MAX(id) FROM syncapi_output_room_events"
 
@@ -121,7 +118,6 @@ type outputRoomEventsStatements struct {
 	selectRecentEventsForSyncStmt *sql.Stmt
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
-	selectStreamPositionForEventIDStmt *sql.Stmt
 }
 
 func (s *outputRoomEventsStatements) prepare(db *sql.DB) (err error) {
@@ -150,16 +146,7 @@ func (s *outputRoomEventsStatements) prepare(db *sql.DB) (err error) {
 	if s.selectStateInRangeStmt, err = db.Prepare(selectStateInRangeSQL); err != nil {
 		return
 	}
-	if s.selectStreamPositionForEventIDStmt, err = db.Prepare(selectStreamPositionForEventIDSQL); err != nil {
 	return
-	}
-	return
-}
-
-func (s *outputRoomEventsStatements) selectStreamPositionForEventID(ctx context.Context, eventID string) (types.StreamPosition, error) {
-	var id int64
-	err := s.selectStreamPositionForEventIDStmt.QueryRowContext(ctx, eventID).Scan(&id)
-	return types.StreamPosition(id), err
 }
 
 // selectStateInRange returns the state events between the two given PDU stream positions, exclusive of oldPos, inclusive of newPos.

syncapi/storage/postgres/output_room_events_topology_table.go

@@ -60,7 +60,7 @@ const selectEventIDsInRangeDESCSQL = "" +
 	" ORDER BY topological_position DESC, stream_position DESC LIMIT $6"
 
 const selectPositionInTopologySQL = "" +
-	"SELECT topological_position FROM syncapi_output_room_events_topology" +
+	"SELECT topological_position, stream_position FROM syncapi_output_room_events_topology" +
 	" WHERE event_id = $1"
 
 	// Select the max topological position for the room, then sort by stream position and take the highest,
@@ -163,8 +163,8 @@ func (s *outputRoomEventsTopologyStatements) selectEventIDsInRange(
 // topology of the room it belongs to.
 func (s *outputRoomEventsTopologyStatements) selectPositionInTopology(
 	ctx context.Context, eventID string,
-) (pos types.StreamPosition, err error) {
+) (pos, spos types.StreamPosition, err error) {
-	err = s.selectPositionInTopologyStmt.QueryRowContext(ctx, eventID).Scan(&pos)
+	err = s.selectPositionInTopologyStmt.QueryRowContext(ctx, eventID).Scan(&pos, &spos)
 	return
 }
 

syncapi/storage/postgres/syncserver.go

@@ -320,12 +320,7 @@ func (d *SyncServerDatasource) EventsAtTopologicalPosition(
 func (d *SyncServerDatasource) EventPositionInTopology(
 	ctx context.Context, eventID string,
 ) (depth types.StreamPosition, stream types.StreamPosition, err error) {
-	depth, err = d.topology.selectPositionInTopology(ctx, eventID)
+	return d.topology.selectPositionInTopology(ctx, eventID)
-	if err != nil {
-		return
-	}
-	stream, err = d.events.selectStreamPositionForEventID(ctx, eventID)
-	return
 }
 
 func (d *SyncServerDatasource) SyncStreamPosition(ctx context.Context) (types.StreamPosition, error) {
@@ -591,8 +586,8 @@ func (d *SyncServerDatasource) getResponseWithPDUsForCompleteSync(
 
 		// Retrieve the backward topology position, i.e. the position of the
 		// oldest event in the room's topology.
-		var backwardTopologyPos types.StreamPosition
+		var backwardTopologyPos, backwardStreamPos types.StreamPosition
-		backwardTopologyPos, err = d.topology.selectPositionInTopology(ctx, recentStreamEvents[0].EventID())
+		backwardTopologyPos, backwardStreamPos, err = d.topology.selectPositionInTopology(ctx, recentStreamEvents[0].EventID())
 		if backwardTopologyPos-1 <= 0 {
 			backwardTopologyPos = types.StreamPosition(1)
 		} else {
@@ -605,7 +600,7 @@ func (d *SyncServerDatasource) getResponseWithPDUsForCompleteSync(
 		stateEvents = removeDuplicates(stateEvents, recentEvents)
 		jr := types.NewJoinResponse()
 		jr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardStreamPos,
 		).String()
 		jr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		jr.Timeline.Limited = true
@@ -720,9 +715,9 @@ func (d *SyncServerDatasource) addInvitesToResponse(
 func (d *SyncServerDatasource) getBackwardTopologyPos(
 	ctx context.Context,
 	events []types.StreamEvent,
-) (pos types.StreamPosition) {
+) (pos, spos types.StreamPosition) {
 	if len(events) > 0 {
-		pos, _ = d.topology.selectPositionInTopology(ctx, events[0].EventID())
+		pos, spos, _ = d.topology.selectPositionInTopology(ctx, events[0].EventID())
 	}
 	if pos-1 <= 0 {
 		pos = types.StreamPosition(1)
@@ -761,14 +756,14 @@ func (d *SyncServerDatasource) addRoomDeltaToResponse(
 	}
 	recentEvents := d.StreamEventsToEvents(device, recentStreamEvents)
 	delta.stateEvents = removeDuplicates(delta.stateEvents, recentEvents) // roll back
-	backwardTopologyPos := d.getBackwardTopologyPos(ctx, recentStreamEvents)
+	backwardTopologyPos, backwardStreamPos := d.getBackwardTopologyPos(ctx, recentStreamEvents)
 
 	switch delta.membership {
 	case gomatrixserverlib.Join:
 		jr := types.NewJoinResponse()
 
 		jr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardStreamPos,
 		).String()
 		jr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		jr.Timeline.Limited = false // TODO: if len(events) >= numRecents + 1 and then set limited:true
@@ -781,7 +776,7 @@ func (d *SyncServerDatasource) addRoomDeltaToResponse(
 		//       no longer in the room.
 		lr := types.NewLeaveResponse()
 		lr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardStreamPos,
 		).String()
 		lr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		lr.Timeline.Limited = false // TODO: if len(events) >= numRecents + 1 and then set limited:true

syncapi/storage/sqlite3/output_room_events_table.go

@@ -74,9 +74,6 @@ const selectEarlyEventsSQL = "" +
 const selectMaxEventIDSQL = "" +
 	"SELECT MAX(id) FROM syncapi_output_room_events"
 
-const selectStreamPositionForEventIDSQL = "" +
-	"SELECT id FROM syncapi_output_room_events WHERE event_id = $1"
-
 // In order for us to apply the state updates correctly, rows need to be ordered in the order they were received (id).
 /*
 	$1 = oldPos,
@@ -110,7 +107,6 @@ type outputRoomEventsStatements struct {
 	selectRecentEventsForSyncStmt *sql.Stmt
 	selectEarlyEventsStmt         *sql.Stmt
 	selectStateInRangeStmt        *sql.Stmt
-	selectStreamPositionForEventIDStmt *sql.Stmt
 }
 
 func (s *outputRoomEventsStatements) prepare(db *sql.DB, streamID *streamIDStatements) (err error) {
@@ -140,16 +136,7 @@ func (s *outputRoomEventsStatements) prepare(db *sql.DB, streamID *streamIDState
 	if s.selectStateInRangeStmt, err = db.Prepare(selectStateInRangeSQL); err != nil {
 		return
 	}
-	if s.selectStreamPositionForEventIDStmt, err = db.Prepare(selectStreamPositionForEventIDSQL); err != nil {
 	return
-	}
-	return
-}
-
-func (s *outputRoomEventsStatements) selectStreamPositionForEventID(ctx context.Context, eventID string) (types.StreamPosition, error) {
-	var id int64
-	err := s.selectStreamPositionForEventIDStmt.QueryRowContext(ctx, eventID).Scan(&id)
-	return types.StreamPosition(id), err
 }
 
 // selectStateInRange returns the state events between the two given PDU stream positions, exclusive of oldPos, inclusive of newPos.

syncapi/storage/sqlite3/output_room_events_topology_table.go

@@ -57,7 +57,7 @@ const selectEventIDsInRangeDESCSQL = "" +
 	" ORDER BY topological_position DESC, stream_position DESC LIMIT $6"
 
 const selectPositionInTopologySQL = "" +
-	"SELECT topological_position FROM syncapi_output_room_events_topology" +
+	"SELECT topological_position, stream_position FROM syncapi_output_room_events_topology" +
 	" WHERE event_id = $1"
 
 const selectMaxPositionInTopologySQL = "" +
@@ -157,9 +157,9 @@ func (s *outputRoomEventsTopologyStatements) selectEventIDsInRange(
 // topology of the room it belongs to.
 func (s *outputRoomEventsTopologyStatements) selectPositionInTopology(
 	ctx context.Context, txn *sql.Tx, eventID string,
-) (pos types.StreamPosition, err error) {
+) (pos types.StreamPosition, spos types.StreamPosition, err error) {
 	stmt := common.TxStmt(txn, s.selectPositionInTopologyStmt)
-	err = stmt.QueryRowContext(ctx, eventID).Scan(&pos)
+	err = stmt.QueryRowContext(ctx, eventID).Scan(&pos, &spos)
 	return
 }
 

syncapi/storage/sqlite3/syncserver.go

@@ -374,12 +374,7 @@ func (d *SyncServerDatasource) EventsAtTopologicalPosition(
 func (d *SyncServerDatasource) EventPositionInTopology(
 	ctx context.Context, eventID string,
 ) (depth types.StreamPosition, stream types.StreamPosition, err error) {
-	depth, err = d.topology.selectPositionInTopology(ctx, nil, eventID)
+	return d.topology.selectPositionInTopology(ctx, nil, eventID)
-	if err != nil {
-		return
-	}
-	stream, err = d.events.selectStreamPositionForEventID(ctx, eventID)
-	return
 }
 
 // SyncStreamPosition returns the latest position in the sync stream. Returns 0 if there are no events yet.
@@ -657,8 +652,8 @@ func (d *SyncServerDatasource) getResponseWithPDUsForCompleteSync(
 
 		// Retrieve the backward topology position, i.e. the position of the
 		// oldest event in the room's topology.
-		var backwardTopologyPos types.StreamPosition
+		var backwardTopologyPos, backwardTopologyStreamPos types.StreamPosition
-		backwardTopologyPos, err = d.topology.selectPositionInTopology(ctx, txn, recentStreamEvents[0].EventID())
+		backwardTopologyPos, backwardTopologyStreamPos, err = d.topology.selectPositionInTopology(ctx, txn, recentStreamEvents[0].EventID())
 		if backwardTopologyPos-1 <= 0 {
 			backwardTopologyPos = types.StreamPosition(1)
 		} else {
@@ -671,7 +666,7 @@ func (d *SyncServerDatasource) getResponseWithPDUsForCompleteSync(
 		stateEvents = removeDuplicates(stateEvents, recentEvents)
 		jr := types.NewJoinResponse()
 		jr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardTopologyStreamPos,
 		).String()
 		jr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		jr.Timeline.Limited = true
@@ -818,10 +813,11 @@ func (d *SyncServerDatasource) addInvitesToResponse(
 func (d *SyncServerDatasource) getBackwardTopologyPos(
 	ctx context.Context, txn *sql.Tx,
 	events []types.StreamEvent,
-) (pos types.StreamPosition) {
+) (pos, spos types.StreamPosition) {
 	if len(events) > 0 {
-		pos, _ = d.topology.selectPositionInTopology(ctx, txn, events[0].EventID())
+		pos, spos, _ = d.topology.selectPositionInTopology(ctx, txn, events[0].EventID())
 	}
+	// TODO: I have no idea what this is doing.
 	if pos-1 <= 0 {
 		pos = types.StreamPosition(1)
 	} else {
@@ -859,14 +855,14 @@ func (d *SyncServerDatasource) addRoomDeltaToResponse(
 	}
 	recentEvents := d.StreamEventsToEvents(device, recentStreamEvents)
 	delta.stateEvents = removeDuplicates(delta.stateEvents, recentEvents)
-	backwardTopologyPos := d.getBackwardTopologyPos(ctx, txn, recentStreamEvents)
+	backwardTopologyPos, backwardStreamPos := d.getBackwardTopologyPos(ctx, txn, recentStreamEvents)
 
 	switch delta.membership {
 	case gomatrixserverlib.Join:
 		jr := types.NewJoinResponse()
 
 		jr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardStreamPos,
 		).String()
 		jr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		jr.Timeline.Limited = false // TODO: if len(events) >= numRecents + 1 and then set limited:true
@@ -879,7 +875,7 @@ func (d *SyncServerDatasource) addRoomDeltaToResponse(
 		//       no longer in the room.
 		lr := types.NewLeaveResponse()
 		lr.Timeline.PrevBatch = types.NewPaginationTokenFromTypeAndPosition(
-			types.PaginationTokenTypeTopology, backwardTopologyPos, 0,
+			types.PaginationTokenTypeTopology, backwardTopologyPos, backwardStreamPos,
 		).String()
 		lr.Timeline.Events = gomatrixserverlib.HeaderedToClientEvents(recentEvents, gomatrixserverlib.FormatSync)
 		lr.Timeline.Limited = false // TODO: if len(events) >= numRecents + 1 and then set limited:true

syncapi/storage/storage_test.go

@@ -220,6 +220,49 @@ func TestSyncResponse(t *testing.T) {
 	}
 }
 
+func TestGetEventsInRangeWithPrevBatch(t *testing.T) {
+	t.Parallel()
+	db := MustCreateDatabase(t)
+	events, _ := SimpleRoom(t, testRoomID, testUserIDA, testUserIDB)
+	positions := MustWriteEvents(t, db, events)
+	latest, err := db.SyncPosition(ctx)
+	if err != nil {
+		t.Fatalf("failed to get SyncPosition: %s", err)
+	}
+	from := types.NewPaginationTokenFromTypeAndPosition(
+		types.PaginationTokenTypeStream, positions[len(positions)-2], types.StreamPosition(0),
+	)
+
+	res, err := db.IncrementalSync(ctx, testUserDeviceA, *from, latest, 5, false)
+	if err != nil {
+		t.Fatalf("failed to IncrementalSync with latest token")
+	}
+	roomRes, ok := res.Rooms.Join[testRoomID]
+	if !ok {
+		t.Fatalf("IncrementalSync response missing room %s - response: %+v", testRoomID, res)
+	}
+	// returns the last event "Message 10"
+	assertEventsEqual(t, "IncrementalSync Timeline", false, roomRes.Timeline.Events, reversed(events[len(events)-1:]))
+
+	prev := roomRes.Timeline.PrevBatch
+	if prev == "" {
+		t.Fatalf("IncrementalSync expected prev_batch token")
+	}
+	prevBatchToken, err := types.NewPaginationTokenFromString(prev)
+	if err != nil {
+		t.Fatalf("failed to NewPaginationTokenFromString : %s", err)
+	}
+	// backpaginate 5 messages starting at the latest position.
+	// head towards the beginning of time
+	to := types.NewPaginationTokenFromTypeAndPosition(types.PaginationTokenTypeTopology, 0, 0)
+	paginatedEvents, err := db.GetEventsInRange(ctx, prevBatchToken, to, testRoomID, 5, true)
+	if err != nil {
+		t.Fatalf("GetEventsInRange returned an error: %s", err)
+	}
+	gots := gomatrixserverlib.HeaderedToClientEvents(db.StreamEventsToEvents(&testUserDeviceA, paginatedEvents), gomatrixserverlib.FormatAll)
+	assertEventsEqual(t, "", true, gots, reversed(events[len(events)-6:len(events)-1]))
+}
+
 // The purpose of this test is to ensure that backfill does indeed go backwards, using a stream token.
 func TestGetEventsInRangeWithStreamToken(t *testing.T) {
 	t.Parallel()