Function exportInternal

worker/export.go:775–944

exportInternal contains the core logic to export a Dgraph database. If skipZero is set to false, the parts of this method that require to talk to zero will be skipped. This is useful when exporting a p directory directly from disk without a running cluster. It uses stream framework to export the dat

(ctx context.Context, in *pb.ExportRequest, db *badger.DB,
	skipZero bool)

// It uses stream framework to export the data. While it uses an iterator for exporting the schema
// and types.
func exportInternal(ctx context.Context, in *pb.ExportRequest, db *badger.DB,
	skipZero bool) (ExportedFiles, error) {

	uts := time.Unix(in.UnixTs, 0)
	exportStorage, err := NewExportStorage(in,
		fmt.Sprintf("dgraph.r%d.u%s", in.ReadTs, uts.UTC().Format("0102.1504")))
	if err != nil {
		return nil, err
	}
	writers, err := InitWriters(exportStorage, in)
	if err != nil {
		return nil, errors.Wrap(err, "exportInternal failed")
	}
	// This stream exports only the data and the graphQL schema.
	stream := db.NewStreamAt(in.ReadTs)
	stream.Prefix = []byte{x.DefaultPrefix}
	if in.Namespace != math.MaxUint64 {
		// Export a specific namespace.
		stream.Prefix = append(stream.Prefix, x.NamespaceToBytes(in.Namespace)...)
	}
	stream.LogPrefix = "Export"
	stream.ChooseKey = func(item *badger.Item) bool {
		// Skip exporting delete data including Schema and Types.
		if item.IsDeletedOrExpired() {
			return false
		}
		pk, err := x.Parse(item.Key())
		if err != nil {
			glog.Errorf("error %v while parsing key %v during export. Skip.", err,
				hex.EncodeToString(item.Key()))
			return false
		}

		// Do not pick keys storing parts of a multi-part list. They will be read
		// from the main key.
		if pk.HasStartUid {
			return false
		}
		// _predicate_ is deprecated but leaving this here so that users with a
		// binary with version >= 1.1 can export data from a version < 1.1 without
		// this internal data showing up.
		if pk.Attr == "_predicate_" {
			return false
		}

		if !skipZero {
			if servesTablet, err := groups().ServesTablet(pk.Attr); err != nil || !servesTablet {
				return false
			}
		}

		if strings.Contains(pk.Attr, hnsw.VecKeyword) {
			return false
		}
		return pk.IsData()
	}

	stream.KeyToList = func(key []byte, itr *badger.Iterator) (*bpb.KVList, error) {