Fix prev_batch tokens (#999)

3 files changed, 19 insertions, 37 deletions

diff --git a/syncapi/storage/postgres/output_room_events_table.go b/syncapi/storage/postgres/output_room_events_table.go
index 769823e9..0b53dfa9 100644
--- a/syncapi/storage/postgres/output_room_events_table.go
+++ b/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"
 
@@ -114,14 +111,13 @@ const selectStateInRangeSQL = "" +
 	" LIMIT $8"
 
 type outputRoomEventsStatements struct {
-	insertEventStmt                    *sql.Stmt
-	selectEventsStmt                   *sql.Stmt
-	selectMaxEventIDStmt               *sql.Stmt
-	selectRecentEventsStmt             *sql.Stmt
-	selectRecentEventsForSyncStmt      *sql.Stmt
-	selectEarlyEventsStmt              *sql.Stmt
-	selectStateInRangeStmt             *sql.Stmt
-	selectStreamPositionForEventIDStmt *sql.Stmt
+	insertEventStmt               *sql.Stmt
+	selectEventsStmt              *sql.Stmt
+	selectMaxEventIDStmt          *sql.Stmt
+	selectRecentEventsStmt        *sql.Stmt
+	selectRecentEventsForSyncStmt *sql.Stmt
+	selectEarlyEventsStmt         *sql.Stmt
+	selectStateInRangeStmt        *sql.Stmt
 }
 
 func (s *outputRoomEventsStatements) prepare(db *sql.DB) (err error) {
@@ -150,18 +146,9 @@ 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.
 // Results are bucketed based on the room ID. If the same state is overwritten multiple times between the
 // two positions, only the most recent state is returned.
diff --git a/syncapi/storage/postgres/output_room_events_topology_table.go b/syncapi/storage/postgres/output_room_events_topology_table.go
index f77365c8..51cbd50d 100644
--- a/syncapi/storage/postgres/output_room_events_topology_table.go
+++ b/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) {
-	err = s.selectPositionInTopologyStmt.QueryRowContext(ctx, eventID).Scan(&pos)
+) (pos, spos types.StreamPosition, err error) {
+	err = s.selectPositionInTopologyStmt.QueryRowContext(ctx, eventID).Scan(&pos, &spos)
 	return
 }
 
diff --git a/syncapi/storage/postgres/syncserver.go b/syncapi/storage/postgres/syncserver.go
index 744ae7b8..a6de1517 100644
--- a/syncapi/storage/postgres/syncserver.go
+++ b/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)
-	if err != nil {
-		return
-	}
-	stream, err = d.events.selectStreamPositionForEventID(ctx, eventID)
-	return
+	return d.topology.selectPositionInTopology(ctx, eventID)
 }
 
 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
-		backwardTopologyPos, err = d.topology.selectPositionInTopology(ctx, recentStreamEvents[0].EventID())
+		var backwardTopologyPos, backwardStreamPos types.StreamPosition
+		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