Remove containsBackwardsExtremity

syncapi/routing/messages.go

@@ -352,54 +352,6 @@ func (r *messagesReq) handleNonEmptyEventsSlice(streamEvents []types.StreamEvent
 	return
 }
 
-// containsBackwardExtremity checks if a slice of StreamEvent contains a
-// backward extremity. It does so by selecting the earliest event in the slice
-// and by checking the presence in the database of all of its parent events, and
-// considers the event itself a backward extremity if at least one of the parent
-// events doesn't exist in the database.
-// Returns an error if there was an issue with talking to the database.
-//
-// This function is unused but currently set to nolint for now until we are
-// absolutely sure that the changes in matrix-org/dendrite#847 are behaving
-// properly.
-// nolint:unused
-func (r *messagesReq) containsBackwardExtremity(events []types.StreamEvent) (bool, error) {
-	// Select the earliest retrieved event.
-	var ev *types.StreamEvent
-	if r.backwardOrdering {
-		ev = &(events[len(events)-1])
-	} else {
-		ev = &(events[0])
-	}
-	// Get the earliest retrieved event's parents.
-	prevIDs := ev.PrevEventIDs()
-	prevs, err := r.db.Events(r.ctx, prevIDs)
-	if err != nil {
-		return false, nil
-	}
-	// Check if we have all of the events we requested. If not, it means we've
-	// reached a backward extremity.
-	var eventInDB bool
-	var id string
-	// Iterate over the IDs we used in the request.
-	for _, id = range prevIDs {
-		eventInDB = false
-		// Iterate over the events we got in response.
-		for _, ev := range prevs {
-			if ev.EventID() == id {
-				eventInDB = true
-			}
-		}
-		// One occurrence of one the event's parents not being present in the
-		// database is enough to say that the event is a backward extremity.
-		if !eventInDB {
-			return true, nil
-		}
-	}
-
-	return false, nil
-}
-
 // backfill performs a backfill request over the federation on another
 // homeserver in the room.
 // See: https://matrix.org/docs/spec/server_server/latest#get-matrix-federation-v1-backfill-roomid