fix(backup): don't backup views

Fixes #3918

pkg/service/backup/model.go

@@ -497,6 +497,16 @@ func (f localDataFilter) filter(_, _ string, ring scyllaclient.Ring) bool {
 	return ring.Replication != scyllaclient.LocalStrategy
 }
 
+// Filters out views as they are restored by re-creating them on restored base table.
+// There is no use in backing up their sstables.
+type viewFilter struct {
+	views *strset.Set
+}
+
+func (f viewFilter) filter(ks, tab string, _ scyllaclient.Ring) bool {
+	return !f.views.Has(ks + "." + tab)
+}
+
 // tableValidator checks if it's safe to back up table.
 type tabValidator interface {
 	validate(ks, tab string, ring scyllaclient.Ring) error

pkg/service/backup/service.go

@@ -28,6 +28,7 @@ import (
 	"github.com/scylladb/scylla-manager/v3/pkg/util/inexlist/ksfilter"
 	"github.com/scylladb/scylla-manager/v3/pkg/util/jsonutil"
 	"github.com/scylladb/scylla-manager/v3/pkg/util/parallel"
+	"github.com/scylladb/scylla-manager/v3/pkg/util/query"
 	"github.com/scylladb/scylla-manager/v3/pkg/util/timeutc"
 	"github.com/scylladb/scylla-manager/v3/pkg/util/uuid"
 	"go.uber.org/atomic"
@@ -161,6 +162,22 @@ func (s *Service) GetTarget(ctx context.Context, clusterID uuid.UUID, properties
 		localDataFilter{},
 	}
 
+	// Try to add view filter - possible only when credentials are set
+	session, err := s.clusterSession(ctx, clusterID)
+	switch {
+	case err == nil:
+		defer session.Close()
+		views, err := query.GetAllViews(session)
+		if err != nil {
+			return Target{}, errors.Wrap(err, "get cluster views")
+		}
+		filters = append(filters, viewFilter{views: views})
+	case errors.Is(err, cluster.ErrNoCQLCredentials):
+		s.logger.Error(ctx, "No CQL cluster credentials, backup of views won't be skipped", "error", err)
+	default:
+		return Target{}, errors.Wrap(err, "create cluster session")
+	}
+
 	validators := []tabValidator{
 		tokenRangesValidator{
 			liveNodes: strset.New(liveNodes.Hosts()...),