reset event checkpoint key properly for non sub-page breaks

lib/events/dynamoevents/dynamoevents.go

@@ -789,7 +789,7 @@ func (l *Log) searchEventsRaw(fromUTC, toUTC time.Time, namespace string, eventT
 	totalSize := 0
 	dates := daysBetween(fromUTC, toUTC)
 	query := "CreatedAtDate = :date AND CreatedAt BETWEEN :start and :end"
-	g := l.WithFields(log.Fields{"From": fromUTC, "To": toUTC, "Namespace": namespace, "EventTypes": eventTypes, "Limit": limit, "StartKey": startKey})
+	g := l.WithFields(log.Fields{"From": fromUTC, "To": toUTC, "Namespace": namespace, "EventTypes": eventTypes, "Limit": limit, "StartKey": startKey, "Order": order})
 	var left int64
 	if limit != 0 {
 		left = int64(limit)
@@ -865,7 +865,8 @@ dateLoop:
 			if err != nil {
 				return nil, "", trace.Wrap(err)
 			}
-			g.WithFields(log.Fields{"duration": time.Since(start), "items": len(out.Items)}).Debugf("Query completed.")
+			g.WithFields(log.Fields{"duration": time.Since(start), "items": len(out.Items), "forward": forward, "iterator": checkpoint.Iterator}).Debugf("Query completed.")
+			oldIterator := checkpoint.Iterator
 			checkpoint.Iterator = out.LastEvaluatedKey
 
 			for _, item := range out.Items {
@@ -896,11 +897,15 @@ dateLoop:
 				// checkpoint is needed for sub-page breaks.
 				if totalSize+len(data) >= events.MaxEventBytesInResponse {
 					hasLeft = i+1 != len(dates) || len(checkpoint.Iterator) != 0
+
 					key, err := getSubPageCheckpoint(&e)
 					if err != nil {
 						return nil, "", trace.Wrap(err)
 					}
 					checkpoint.EventKey = key
+
+					// We need to reset the iterator so we get the previous page again.
+					checkpoint.Iterator = oldIterator
 					break dateLoop
 				}
 
@@ -910,6 +915,7 @@ dateLoop:
 
 				if left == 0 {
 					hasLeft = i+1 != len(dates) || len(checkpoint.Iterator) != 0
+					checkpoint.EventKey = ""
 					break dateLoop
 				}
 			}